It's the turn of the year, so Bash wants to send presents to his friends. There are n cities in the Himalayan region and they are connected by m bidirectional roads. Bash is living in city s. Bash has exactly one friend in each of the other cities. Since Bash wants to surprise his friends, he decides to send a Pikachu to each of them. Since there may be some cities which are not reachable from Bash's city, he only sends a Pikachu to those friends who live in a city reachable from his own city. He also wants to send it to them as soon as possible.

He finds out the minimum time for each of his Pikachus to reach its destination city. Since he is a perfectionist, he informs all his friends with the time their gift will reach them. A Pikachu travels at a speed of 1 meters per second. His friends were excited to hear this and would be unhappy if their presents got delayed. Unfortunately Team Rocket is on the loose and they came to know of Bash's plan. They want to maximize the number of friends who are unhappy with Bash.

They do this by destroying exactly one of the other n - 1 cities. This implies that the friend residing in that city dies, so he is unhappy as well.

Note that if a city is destroyed, all the roads directly connected to the city are also destroyed and the Pikachu may be forced to take a longer alternate route.

Please also note that only friends that are waiting for a gift count as unhappy, even if they die.

Since Bash is already a legend, can you help Team Rocket this time and find out the maximum number of Bash's friends who can be made unhappy by destroying exactly one city.

Input

The first line contains three space separated integers n, m and s (2 ≤ n ≤ 2·105, <image>, 1 ≤ s ≤ n) — the number of cities and the number of roads in the Himalayan region and the city Bash lives in.

Each of the next m lines contain three space-separated integers u, v and w (1 ≤ u, v ≤ n, u ≠ v, 1 ≤ w ≤ 109) denoting that there exists a road between city u and city v of length w meters.

It is guaranteed that no road connects a city to itself and there are no two roads that connect the same pair of cities.

Output

Print a single integer, the answer to the problem.

Examples

Input

4 4 3
1 2 1
2 3 1
2 4 1
3 1 1


Output

2


Input

7 11 2
1 2 5
1 3 5
2 4 2
2 5 2
3 6 3
3 7 3
4 6 2
3 4 2
6 7 3
4 5 7
4 7 7


Output

4

Note

In the first sample, on destroying the city 2, the length of shortest distance between pairs of cities (3, 2) and (3, 4) will change. Hence the answer is 2.
#include <bits/stdc++.h>
using namespace std;
template <class T>
using min_queue = priority_queue<T, vector<T>, greater<T>>;
const int INF = static_cast<int>(1e9);
const long long INF_LL = static_cast<long long>(4e18);
const double pi = acos(-1.0);
template <class T>
inline T& smin(T& x, const T& y) {
  return x > y ? x = y : x;
}
template <class T>
inline T& smax(T& x, const T& y) {
  return x < y ? x = y : x;
}
template <class T>
inline T sqr(const T& x) {
  return x * x;
}
template <class T>
inline int sgn(const T& x) {
  return (T(0) < x) - (x < T(0));
}
template <class T>
T gcd(T a, T b) {
  for (a = abs(a), b = abs(b); a && b; a >= b ? a %= b : b %= a)
    ;
  return a + b;
}
using uint = unsigned int;
const uint BUFFER_SIZE = 1 << 12;
const uint MAX_LENGTH = 1 << 7;
namespace Detail {
struct Width {
  uint value;
};
struct Fill {
  char value;
};
struct Base {
  uint value;
};
struct Precision {
  uint value;
};
struct Delimiter {
  const char* value;
};
}  // namespace Detail
Detail::Width setWidth(uint value = 0) { return {value}; }
Detail::Fill setFill(char value = ' ') { return {value}; }
Detail::Base setBase(uint value = 10) {
  assert(2 <= value && value <= 36);
  return {value};
}
Detail::Precision setPrecision(uint value = 9) {
  assert(value < MAX_LENGTH);
  return {value};
}
Detail::Delimiter setDelimiter(const char* value = " ") { return {value}; }
class InputDevice {
 protected:
  const char* head;
  const char* tail;
  InputDevice(const char* head, const char* tail)
      : head(head), tail(tail), base(setBase().value) {}
  virtual void fillInput() = 0;
  inline char nextChar() {
    if (__builtin_expect(head >= tail, false)) fillInput();
    return *head++;
  }
  template <class I>
  int readUnsignedIntGeneral(I& arg, char c) {
    I value = 0;
    int length = 0;
    for (;; ++length, c = nextChar()) {
      if (isDigit(c))
        c -= '0';
      else if (isUpper(c))
        c -= 'A' - 10;
      else if (isLower(c))
        c -= 'a' - 10;
      else
        c = base;
      if (c >= base) break;
      value = base * value + c;
    }
    arg = value;
    return --head, length;
  }
  template <class I>
  inline int readUnsignedInt(I& arg, char c) {
    if (__builtin_expect(base > 10, false))
      return readUnsignedIntGeneral(arg, c);
    I value = 0;
    int length = 0;
    for (; static_cast<unsigned char>(c - '0') < base; ++length, c = nextChar())
      value = base * value + c - '0';
    arg = value;
    return --head, length;
  }
  template <class I>
  inline bool readSignedInt(I& arg, char c) {
    bool negative = c == '-';
    if (negative) c = nextChar();
    typename make_unsigned<I>::type unsignedArg;
    if (readUnsignedInt(unsignedArg, c) == 0) return false;
    arg = negative ? ~static_cast<I>(unsignedArg - 1)
                   : static_cast<I>(unsignedArg);
    return true;
  }
  template <class F>
  bool readFloatingPoint(F& arg, char c) {
    bool negative = c == '-';
    if (negative) c = nextChar();
    unsigned long long integerPart;
    if (readUnsignedInt(integerPart, c) == 0) return false;
    arg = static_cast<F>(integerPart);
    if (nextChar() == '.') {
      unsigned long long fractionalPart = 0;
      int fractionalLength = readUnsignedInt(fractionalPart, nextChar());
      if (fractionalLength > 0) {
        unsigned long long basePower = 1;
        for (; fractionalLength; --fractionalLength) basePower *= base;
        arg += static_cast<F>(fractionalPart) / basePower;
      }
    } else
      --head;
    if (negative) arg = -arg;
    return true;
  }

 public:
  uint base;
  InputDevice(InputDevice const&) = delete;
  InputDevice& operator=(InputDevice const&) = delete;
  static inline bool isSpace(char c) {
    return static_cast<unsigned char>(c - '\t') < 5 || c == ' ';
  }
  static inline bool isDigit(char c) {
    return static_cast<unsigned char>(c - '0') < 10;
  }
  static inline bool isUpper(char c) {
    return static_cast<unsigned char>(c - 'A') < 26;
  }
  static inline bool isLower(char c) {
    return static_cast<unsigned char>(c - 'a') < 26;
  }
  static inline bool isOneOf(char c, const char* str) {
    return strchr(str, c) != nullptr;
  }
  void putBack() { --head; }
  inline bool readChar(char& arg) {
    if (__builtin_expect(head >= tail, false)) {
      fillInput();
      if (__builtin_expect(head >= tail, false)) return arg = '\0', false;
    }
    return arg = *head++, true;
  }
  template <class UnaryPredicate>
  inline char skipCharacters(UnaryPredicate isSkipped) {
    char c;
    do {
      c = nextChar();
    } while (isSkipped(c));
    return c;
  }
  inline char skipCharacters() { return skipCharacters(isSpace); }
  template <class UnaryPredicate>
  inline bool readString(char* arg, int limit, UnaryPredicate isTerminator) {
    skipCharacters(isTerminator);
    for (--head, --limit; head < tail; fillInput()) {
      ptrdiff_t chunkSize =
          find_if(head, min(tail, head + limit), isTerminator) - head;
      arg = copy_n(head, chunkSize, arg);
      head += chunkSize;
      limit -= chunkSize;
      if (chunkSize == 0 || head < tail) break;
    }
    return *arg = '\0', true;
  }
  template <class I>
  inline bool readUnsignedInt(I& arg) {
    return readUnsignedInt(arg, skipCharacters()) > 0;
  }
  template <class I>
  inline bool readSignedInt(I& arg) {
    return readSignedInt(arg, skipCharacters());
  }
  template <class F>
  inline bool readFloatingPoint(F& arg) {
    return readFloatingPoint(arg, skipCharacters());
  }
};
class InputFile : public InputDevice {
  FILE* file;
  bool lineBuffered;
  bool owner;
  char buffer[BUFFER_SIZE];
  void fillInput() override {
    head = buffer;
    *buffer = '\0';
    if (__builtin_expect(!lineBuffered, true)) {
      tail = head + fread(buffer, 1, BUFFER_SIZE, file);
    } else {
      tail = head;
      if (fgets(buffer, BUFFER_SIZE, file))
        while (*tail) ++tail;
    }
  }

 public:
  InputFile(FILE* file = stdin, bool lineBuffered = true,
            bool takeOwnership = false)
      : InputDevice(buffer, buffer),
        file(file),
        lineBuffered(lineBuffered),
        owner(takeOwnership) {}
  InputFile(const char* fileName)
      : InputFile(fopen(fileName, "r"), false, true) {}
  ~InputFile() {
    if (owner) fclose(file);
  }
};
class InputString : public InputDevice {
  void fillInput() override {
    while (*tail) ++tail;
  }

 public:
  InputString(const string& s) : InputDevice(s.data(), s.data() + s.size()) {}
  InputString(const char* s) : InputDevice(s, s + strlen(s)) {}
};
class OutputDevice {
 protected:
  char buffer[BUFFER_SIZE + MAX_LENGTH];
  char* output;
  char* end;
  bool separate;
  OutputDevice()
      : output(buffer),
        end(buffer + BUFFER_SIZE + MAX_LENGTH),
        separate(false),
        width(setWidth().value),
        fill(setFill().value),
        base(setBase().value),
        precision(setPrecision().value),
        delimiter(setDelimiter().value) {
    computeBasePower();
  }
  virtual void writeToDevice(uint count) = 0;
  inline void flushMaybe() {
    if (__builtin_expect(output >= buffer + BUFFER_SIZE, false)) {
      writeToDevice(BUFFER_SIZE);
      output = copy(buffer + BUFFER_SIZE, output, buffer);
    }
  }
  template <class I>
  inline char* writeUnsignedInt(I arg, char* last) {
    if (__builtin_expect(arg == 0, false)) *--last = '0';
    if (__builtin_expect(base == 10, true)) {
      for (; arg; arg /= 10) *--last = '0' + arg % 10;
    } else
      for (; arg; arg /= base) {
        I digit = arg % base;
        *--last = digit < 10 ? '0' + digit : 'A' - 10 + digit;
      }
    return last;
  }
  template <class I>
  inline char* writeSignedInt(I arg, char* last) {
    auto unsignedArg = static_cast<typename make_unsigned<I>::type>(arg);
    if (arg < 0) {
      last = writeUnsignedInt(~unsignedArg + 1, last);
      *--last = '-';
      return last;
    }
    return writeUnsignedInt(unsignedArg, last);
  }
  template <class F>
  char* writeFloatingPoint(F arg, char* last) {
    bool negative = signbit(arg);
    if (negative) arg = -arg;
    if (isnan(arg))
      for (int i = 0; i < 3; ++i) *--last = i["NaN"];
    else if (isinf(arg))
      for (int i = 0; i < 3; ++i) *--last = i["fnI"];
    else {
      auto integerPart = static_cast<unsigned long long>(arg);
      auto fractionalPart = static_cast<unsigned long long>(
          (arg - integerPart) * basePower + F(0.5));
      if (fractionalPart >= basePower) ++integerPart, fractionalPart = 0;
      char* point = last - precision;
      if (precision > 0) {
        ::fill(point, writeUnsignedInt(fractionalPart, last), '0');
        *--point = '.';
      }
      last = writeUnsignedInt(integerPart, point);
    }
    if (negative) *--last = '-';
    return last;
  }
  inline int writeT(char* first) {
    int delimiterLenght = separate ? writeDelimiter() : 0;
    separate = true;
    int charsWritten = static_cast<int>(end - first);
    if (__builtin_expect(charsWritten < width, false))
      charsWritten += writeFill(width - charsWritten);
    output = copy(first, end, output);
    flushMaybe();
    return delimiterLenght + charsWritten;
  }
  inline int writeFill(int count) {
    int result = count;
    if (__builtin_expect(output + count + MAX_LENGTH < end, true)) {
      if (count == 1)
        *output++ = fill;
      else
        output = fill_n(output, count, fill);
    } else
      for (uint chunkSize = static_cast<uint>(buffer + BUFFER_SIZE - output);;
           chunkSize = BUFFER_SIZE) {
        if (chunkSize > count) chunkSize = count;
        output = fill_n(output, chunkSize, fill);
        flushMaybe();
        if ((count -= chunkSize) == 0) break;
      }
    return result;
  }

 public:
  int width;
  char fill;
  uint base;
  uint precision;
  unsigned long long basePower;
  string delimiter;
  OutputDevice(OutputDevice const&) = delete;
  OutputDevice& operator=(OutputDevice const&) = delete;
  virtual ~OutputDevice(){};
  void computeBasePower() {
    basePower = 1;
    for (uint i = 0; i < precision; ++i) basePower *= base;
  }
  inline int writeChar(char arg) {
    separate = false;
    *output++ = arg;
    flushMaybe();
    return 1;
  }
  inline int writeString(const char* arg, int count, bool checkWidth = true) {
    separate = false;
    int result =
        count + (checkWidth && count < width ? writeFill(width - count) : 0);
    if (__builtin_expect(output + count + MAX_LENGTH < end, true)) {
      if (count == 1)
        *output++ = *arg;
      else
        output = copy_n(arg, count, output);
    } else
      for (int chunkSize = static_cast<int>(buffer + BUFFER_SIZE - output);;
           chunkSize = BUFFER_SIZE) {
        if (chunkSize > count) chunkSize = count;
        output = copy_n(arg, chunkSize, output);
        flushMaybe();
        if ((count -= chunkSize) == 0) break;
        arg += chunkSize;
      }
    return result;
  }
  inline int writeDelimiter() {
    return writeString(delimiter.c_str(), static_cast<int>(delimiter.size()),
                       false);
  }
  template <class I>
  inline int writeUnsignedInt(I arg) {
    return writeT(writeUnsignedInt(arg, end));
  }
  template <class I>
  inline int writeSignedInt(I arg) {
    return writeT(writeSignedInt(arg, end));
  }
  template <class F>
  inline int writeFloatingPoint(F arg) {
    return writeT(writeFloatingPoint(arg, end));
  }
  inline void flush() {
    writeToDevice(static_cast<uint>(output - buffer));
    output = buffer;
  }
};
class OutputFile : public OutputDevice {
  FILE* file;
  bool owner;
  void writeToDevice(uint count) override {
    fwrite(buffer, 1, count, file);
    fflush(file);
  }

 public:
  OutputFile(FILE* file = stdout, bool takeOwnership = false)
      : file(file), owner(takeOwnership) {}
  OutputFile(const char* fileName) : OutputFile(fopen(fileName, "w"), true) {}
  ~OutputFile() override {
    flush();
    if (owner) fclose(file);
  }
};
class OutputString : public OutputDevice {
  string& str;
  void writeToDevice(uint count) override { str.append(buffer, count); }

 public:
  OutputString(string& str) : OutputDevice(), str(str) {}
  ~OutputString() override { flush(); }
};
unique_ptr<InputFile> input;
unique_ptr<OutputFile> output;
inline int read(Detail::Base base) {
  input->base = base.value;
  return 0;
}
inline int read() { return 0; }
inline int read(char& arg) { return input->readChar(arg); }
template <class I>
inline typename enable_if<is_integral<I>::value && is_unsigned<I>::value,
                          int>::type
read(I& arg) {
  return input->readUnsignedInt(arg);
}
template <class I>
inline
    typename enable_if<is_integral<I>::value && is_signed<I>::value, int>::type
    read(I& arg) {
  return input->readSignedInt(arg);
}
template <class F>
inline typename enable_if<is_floating_point<F>::value, int>::type read(F& arg) {
  return input->readFloatingPoint(arg);
}
inline int read(const char& arg) {
  input->skipCharacters([arg](char c) { return arg != c; });
  return 0;
}
inline int read(const char* arg) {
  if (*arg)
    input->skipCharacters(
        [arg](char c) { return InputDevice::isOneOf(c, arg); });
  else
    input->skipCharacters();
  input->putBack();
  return 0;
}
inline int read(bool (*isSkipped)(char)) {
  input->skipCharacters(isSkipped);
  input->putBack();
  return 0;
}
template <class... Ts>
int read(char* arg, int limit, bool (*isTerminator)(char), Ts&&... args);
template <class... Ts>
int read(char* arg, int limit, const char* terminators, Ts&&... args);
template <class Iterator, class... Ts,
          typename = decltype(*std::declval<Iterator>())>
int read(Iterator first, Iterator last, Ts&&... args);
template <class Iterator, class... Ts,
          typename = decltype(*std::declval<Iterator>())>
int read(Iterator first, int count, Ts&&... args);
template <class T0, class T1, class... Ts,
          typename =
              typename enable_if<!is_convertible<T0, char*>::value, void>::type>
int read(T0&& arg0, T1&& arg1, Ts&&... args);
inline int read(char* arg, int limit, const char* terminators = "") {
  if (!*terminators)
    return input->readString(arg, limit, InputDevice::isSpace);
  else
    return input->readString(arg, limit, [terminators](char c) {
      return InputDevice::isOneOf(c, terminators);
    });
}
template <class... Ts>
inline int read(char* first, char* last, Ts&&... args) {
  return read(first, static_cast<int>(last - first), forward<Ts>(args)...);
}
template <int N, class... Ts>
inline int read(char (&arg)[N], Ts&&... args) {
  return read(static_cast<char*>(arg), N, forward<Ts>(args)...);
}
template <class... Ts>
inline int read(char* arg, int limit, bool (*isTerminator)(char),
                Ts&&... args) {
  int argsRead = input->readString(arg, limit, isTerminator);
  return argsRead + read(forward<Ts>(args)...);
}
template <class... Ts>
inline int read(char* arg, int limit, const char* terminators, Ts&&... args) {
  int argsRead = read(arg, limit, terminators);
  return argsRead + read(forward<Ts>(args)...);
}
template <class T1, class T2>
inline int read(pair<T1, T2>& arg) {
  return read(arg.first) == 1 && read(arg.second) == 1 ? 1 : 0;
}
template <class T>
inline int read(vector<T>& arg) {
  uint n;
  if (read(n) == 0) return 0;
  arg.resize(n);
  return read(arg.begin(), arg.end());
}
template <class Iterator, class... Ts, typename>
int read(Iterator first, Iterator last, Ts&&... args) {
  int success = 1;
  for (; first != last; ++first) success &= read(*first);
  return success + read(forward<Ts>(args)...);
}
template <class Iterator, class... Ts, typename>
int read(Iterator first, int count, Ts&&... args) {
  return read(first, first + count, forward<Ts>(args)...);
}
template <class T0, class T1, class... Ts, typename>
inline int read(T0&& arg0, T1&& arg1, Ts&&... args) {
  int argsRead = read(forward<T0>(arg0));
  return argsRead + read(forward<T1>(arg1), forward<Ts>(args)...);
}
inline int write(Detail::Width width) {
  output->width = static_cast<int>(width.value);
  return 0;
}
inline int write(Detail::Fill fill) {
  output->fill = fill.value;
  return 0;
}
inline int write(Detail::Base base) {
  output->base = base.value;
  output->computeBasePower();
  return 0;
}
inline int write(Detail::Precision precision) {
  output->precision = precision.value;
  output->computeBasePower();
  return 0;
}
inline int write(Detail::Delimiter delimiter) {
  output->delimiter = delimiter.value;
  return 0;
}
inline int write() { return 0; }
inline int write(char arg) { return output->writeChar(arg); }
template <class I>
inline typename enable_if<is_integral<I>::value && is_unsigned<I>::value,
                          int>::type
write(I arg) {
  return output->writeUnsignedInt(arg);
}
template <class I>
inline
    typename enable_if<is_integral<I>::value && is_signed<I>::value, int>::type
    write(I arg) {
  return output->writeSignedInt(arg);
}
template <class F>
inline typename enable_if<is_floating_point<F>::value, int>::type write(F arg) {
  return output->writeFloatingPoint(arg);
}
inline int write(const char* arg) {
  return output->writeString(arg, static_cast<int>(strlen(arg)));
}
template <int N>
inline int write(char (&arg)[N]) {
  return output->writeString(arg, static_cast<int>(strlen(arg)));
}
inline int write(const string& arg) {
  return output->writeString(arg.c_str(), static_cast<int>(arg.size()));
}
template <class T1, class T2>
inline int write(const pair<T1, T2>& arg) {
  int charsWritten = write(arg.first);
  charsWritten += output->writeDelimiter();
  return charsWritten + write(arg.second);
}
template <
    class Iterator, class... Ts,
    typename = typename enable_if<!is_convertible<Iterator, const char*>::value,
                                  decltype(*std::declval<Iterator>())>::type>
int write(Iterator first, Iterator last, Ts&&... args);
template <
    class Iterator, class... Ts,
    typename = typename enable_if<!is_convertible<Iterator, const char*>::value,
                                  decltype(*std::declval<Iterator>())>::type>
int write(Iterator first, int count, Ts&&... args);
template <class T, class T2, class... Ts>
int write(T&& arg, T2&& arg2, Ts&&... args);
template <class Iterator, class... Ts, typename>
int write(Iterator first, Iterator last, Ts&&... args) {
  int charsWritten = 0;
  for (; first != last;
       charsWritten += ++first == last ? 0 : output->writeDelimiter())
    charsWritten += write(*first);
  return charsWritten + write(forward<Ts>(args)...);
}
template <class Iterator, class... Ts, typename>
int write(Iterator first, int count, Ts&&... args) {
  return write(first, first + count, forward<Ts>(args)...);
}
template <class T, class T2, class... Ts>
inline int write(T&& arg, T2&& arg2, Ts&&... args) {
  int charsWritten = write(forward<T>(arg));
  return charsWritten + write(forward<T2>(arg2), forward<Ts>(args)...);
}
template <class... Ts>
inline int writeln(Ts&&... args) {
  return write(forward<Ts>(args)..., '\n');
}
void flush() { output->flush(); }
template <class T>
struct Dijkstra {
  vector<T> dist;
  vector<int> parent;
  template <class G>
  T findDist(const G& graph, int s, int t = -1) {
    dist.assign(graph.size(), numeric_limits<T>::max());
    dist[s] = T();
    parent.assign(graph.size(), -1);
    min_queue<pair<T, int>> queue;
    queue.emplace(dist[s], s);
    while (!queue.empty()) {
      auto pair = queue.top();
      queue.pop();
      int v = pair.second;
      if (v == t) return dist[t];
      if (dist[v] < pair.first) continue;
      for (auto&& edge : graph[v]) {
        int u = edge.first;
        T uDist = dist[v] + edge.second;
        if (uDist < dist[u]) {
          dist[u] = uDist;
          parent[u] = v;
          queue.emplace(uDist, u);
        }
      }
    }
    return numeric_limits<T>::max();
  }
};
template <int N>
struct Log2 {
  enum { value = 1 + Log2<N / 2>::value };
};
template <>
struct Log2<0> {
  enum { value = 0 };
};
template <class T, int V>
class LCA {
  static const int L = Log2<V>::value;
  int depth[V];
  int parent[V][L];
  T data[V][L];
  template <class G>
  void dfs(const G& graph, int v) {
    for (auto&& edge : graph[v])
      if (depth[edge.first] == -1) {
        addEdge(v, edge);
        dfs(graph, edge.first);
      }
  }

 public:
  template <class G>
  void build(const G& graph) {
    fill_n(depth, graph.size(), -1);
    for (int i = 0; i < graph.size(); ++i)
      if (depth[i] == -1) {
        depth[i] = 0;
        dfs(graph, i);
      }
  }
  void addEdge(int v, const pair<int, T>& edge) {
    int u = edge.first;
    depth[u] = v == -1 ? 0 : depth[v] + 1;
    data[u][0] = edge.second;
    fill_n(parent[u], L, -1);
    int w = parent[u][0] = v;
    for (int j = 0; w != -1 && j + 1 < L; ++j) {
      data[u][j + 1] = data[u][j] + data[w][j];
      parent[u][j + 1] = w = parent[w][j];
    }
  }
  int getParent(int v) const { return parent[v][0]; }
  pair<int, T> lca(int u, int v) {
    T res{};
    if (depth[u] < depth[v]) swap(u, v);
    for (int d = depth[u] - depth[v], j = 0; d; d >>= 1, ++j)
      if (d & 1) {
        res += data[u][j];
        u = parent[u][j];
      }
    if (u == v) return {u, res};
    for (int j = L - 1; j >= 0; --j)
      if (parent[u][j] != parent[v][j]) {
        res += data[u][j] + data[v][j];
        u = parent[u][j];
        v = parent[v][j];
      }
    if (parent[u][0] == -1 || parent[u][0] != parent[v][0]) return {-1, T()};
    return {parent[u][0], res + data[u][0] + data[v][0]};
  }
};
template <int V, bool ORIENTED = false>
class GraphUL {
  int n, m;
  vector<int> adjacent[V];

 public:
  GraphUL(int size = 0, int newm = -1) : n(0) { init(size, newm); }
  void init(int size, int newm = -1) {
    for (int i = 0; i < n; ++i) vector<int>().swap(adjacent[i]);
    n = size;
    m = newm >= 0 ? newm : n;
  }
  void addEdge(int u, int v) {
    assert(u < n && v < m);
    adjacent[u].push_back(v);
    if (!ORIENTED && u != v) adjacent[v].push_back(u);
  }
  bool oriented() const { return ORIENTED; }
  int size() const { return n; }
  int size2() const { return m; }
  const vector<int>& operator[](int v) const { return adjacent[v]; }
};
template <class T, int V, bool ORIENTED = false>
class GraphWL {
  int n, m;
  vector<pair<int, T>> adjacent[V];

 public:
  using DataType = T;
  GraphWL(int size = 0, int newm = -1) : n(0) { init(size, newm); }
  void init(int size, int newm = -1) {
    for (int i = 0; i < n; ++i) vector<pair<int, T>>().swap(adjacent[i]);
    n = size;
    m = newm >= 0 ? newm : n;
  }
  void addEdge(int u, int v, const T& weight) {
    assert(u < n && v < n);
    adjacent[u].emplace_back(v, weight);
    if (!ORIENTED && u != v) adjacent[v].emplace_back(u, weight);
  }
  bool oriented() const { return ORIENTED; }
  int size() const { return n; }
  int size2() const { return m; }
  const vector<pair<int, T>>& operator[](int v) const { return adjacent[v]; }
};
int ans = 0;
template <class T, int V>
class DominatorTree {
  Dijkstra<T> paths;
  LCA<bool, V> lca;

 public:
  GraphUL<V> tree;
  template <class Graph>
  void build(const Graph& graph, int s) {
    paths.findDist(graph, s);
    vector<int> topo;
    for (int v = 0; v < graph.size(); ++v)
      if (paths.dist[v] != numeric_limits<typename Graph::DataType>::max())
        topo.push_back(v);
    sort(topo.begin(), topo.end(),
         [this](int u, int v) { return paths.dist[u] < paths.dist[v]; });
    tree.init(static_cast<int>(topo.size()));
    for (int v : topo) {
      int dominator = -1;
      for (auto&& edge : graph[v]) {
        int u = edge.first;
        if (paths.dist[v] == paths.dist[u] + edge.second) {
          if (dominator == -1)
            dominator = u;
          else
            dominator = lca.lca(u, dominator).first;
        }
      }
      lca.addEdge(dominator, {v, false});
    }
    vector<int> subtree(graph.size(), 1);
    for (int i = static_cast<int>((topo).size()) - 1; i >= 0; --i) {
      int v = topo[i];
      if (v != s) smax(ans, subtree[v]);
      int u = lca.getParent(v);
      if (u != -1) subtree[u] += subtree[v];
    }
  }
};
template <class Graph, typename T = typename Graph::DataType>
int read(Graph& graph, int edges = -1, int zero = 1) {
  if (edges == -1 && read(edges) == 0) return 0;
  for (; edges-- > 0;) {
    int u, v;
    T weight;
    if (read(u, v, weight) != 3) return 0;
    graph.addEdge(u - zero, v - zero, weight);
  }
  return 1;
}
const int N = 2e5 + 5;
int n, m, s;
GraphWL<long long, N> graph;
DominatorTree<long long, N> domi;
int main() {
  input.reset(new InputFile(stdin, false));
  output.reset(new OutputFile());
  read(n, m, s);
  graph.init(n);
  read(graph, m);
  domi.build(graph, s - 1);
  writeln(ans);
  return 0;
}
