#include <bits/stdc++.h>
using namespace std;
template <class T>
void splitstr(const string &s, vector<T> &out) {
  istringstream in(s);
  out.clear();
  copy(istream_iterator<T>(in), istream_iterator<T>(), back_inserter(out));
}
template <class T>
T readValue(string s) {
  T result;
  istringstream sin(s);
  sin >> result;
  return result;
}
template <class T>
void initArray(T *arr, int size, T value) {
  for (int i = 0; i < size; i++) arr[i] = value;
}
template <class T>
inline T gcd(T a, T b) {
  return (!a) ? b : gcd(b % a, a);
}
template <class T>
inline T mod(T a, T p) {
  a %= p;
  return (a < 0) ? a + p : a;
}
template <class T>
inline int num_bits(T n) {
  return (!n) ? 0 : 1 + numbits(n & (n - 1));
}
template <class T>
inline T inverse(T a, T m) {
  a = mod<T>(a, m);
  return (a == 1) ? 1 : mod((1 - m * inverse(m % a, a)) / a, m);
}
template <class T>
inline bool is_prime(T a) {
  T lim = (T)sqrt((double)a);
  for (T i = 2; i <= T(lim + 1E-9); i++)
    if (a % i == 0) return false;
  return true;
}
template <class T>
inline T power(T a, T p, T mod) {
  if (!p) return 1;
  T temp = power(a, p >> 1, mod);
  temp = (temp * temp) % mod;
  if (p & 1) temp = (temp * a) % mod;
  return temp;
}
void get_primes(int start, int end, vector<int> &vi) {
  int *p = new int[end + 1];
  initArray<int>(p, end + 1, 0);
  p[1] = 1;
  for (int i = 2; i <= end; i++) {
    if (!p[i]) {
      if (i >= start) vi.push_back(i);
      for (int j = 2 * i; j <= end; j += i) p[j] = 1;
    }
  }
  delete[] p;
}
bool dfs(int current, int final, int total, int *visited, int **edges,
         bool flow) {
  if (current == final) return true;
  if (visited[current]) return false;
  visited[current] = true;
  for (int i = 0; i < total; i++)
    if (edges[current][i] && dfs(i, final, total, visited, edges, flow)) {
      if (flow) {
        edges[current][i]--;
        edges[i][current]++;
      }
      return true;
    }
  return false;
}
int flow(int in, int out, int total, int **edges) {
  int result = 0;
  int *visited = new int[total];
  while (initArray<int>(visited, total, 0),
         dfs(in, out, total, visited, edges, true))
    result++;
  delete[] visited;
  return result;
}
void create_set(int x, int *P, int *rank) {
  P[x] = x;
  rank[x] = 0;
}
int find_set(int x, int *P) {
  if (x != P[x]) P[x] = find_set(P[x], P);
  return P[x];
}
bool merge_sets(int x, int y, int *P, int *rank) {
  int Px = find_set(x, P);
  int Py = find_set(y, P);
  if (Px == Py) return false;
  if (rank[Px] > rank[Py])
    P[Py] = Px;
  else
    P[Px] = Py;
  if (rank[Px] == rank[Py]) rank[Py]++;
  return true;
}
template <typename T>
int read_cum_freq(int index, T *tree) {
  int sum = 0;
  while (index) {
    sum += tree[index];
    index -= (index & -index);
  }
  return sum;
}
template <typename T>
void upd_freq(int index, int mxIndex, int value, T *tree) {
  while (index <= mxIndex) {
    tree[index] += value;
    index += (index & -index);
  }
}
template <typename T>
int read_freq(int index, T *tree) {
  return read_cum_freq(index, tree) - read_cum_freq(index - 1, tree);
}
void build_failure_function(const string &str, int *temp_arr) {
  temp_arr[0] = temp_arr[1] = 0;
  for (int i = 2; i <= ((int)(str).size()); i++) {
    temp_arr[i] = -1;
    for (int ind = temp_arr[i - 1]; temp_arr[i] == -1; ind = temp_arr[ind]) {
      if (str[ind] == str[i - 1]) {
        temp_arr[i] = ind + 1;
      } else if (ind == 0) {
        temp_arr[i] = 0;
      }
    }
  }
}
void KMP(const string &text, const string &pattern, int *res) {
  int *temp_arr = new int[((int)(pattern).size()) + 1];
  build_failure_function(pattern, temp_arr);
  int i = 0;
  int ind = 0;
  while (i < ((int)(text).size())) {
    if (text[i] == pattern[ind]) {
      res[i] = ++ind;
      if (res[i] == ((int)(pattern).size())) {
        ind = temp_arr[ind];
      }
      i++;
    } else if (ind == 0) {
      res[i++] = 0;
    } else {
      ind = temp_arr[ind];
    }
  }
  delete[] temp_arr;
}
void setup(int value, string name) {
  string name_in = name + ".in";
  string name_out = name + ".out";
  freopen(name_in.c_str(), "r", stdin);
  if (value) {
    freopen(name_out.c_str(), "w", stdout);
  }
}
bool arr[1001];
int main() {
  int n;
  std::cin >> n;
  int m;
  std::cin >> m;
  cin.get();
  memset(arr, 0, sizeof(arr));
  for (int j = 0; j < m; j++) {
    string str;
    getline(cin, str);
    int val = atoi(str.substr(str.find("of") + 3).c_str()) - 1;
    if (str.find("left") != string::npos) {
      for (int i = val; i < 1001; i++) arr[i] = true;
    } else {
      for (int i = 0; i <= val; i++) arr[i] = true;
    }
  }
  int res = 0;
  for (int i = 0; i < n; i++)
    if (!arr[i]) res++;
  if (res)
    std::cout << res << std::endl;
  else
    std::cout << -1 << std::endl;
  return 0;
}

### Prompt

Develop a solution in cpp to the problem described below:

<image>

One morning the Cereal Guy found out that all his cereal flakes were gone. He found a note instead of them. It turned out that his smart roommate hid the flakes in one of n boxes. The boxes stand in one row, they are numbered from 1 to n from the left to the right. The roommate left hints like "Hidden to the left of the i-th box" ("To the left of i"), "Hidden to the right of the i-th box" ("To the right of i"). Such hints mean that there are no flakes in the i-th box as well. The Cereal Guy wants to know the minimal number of boxes he necessarily needs to check to find the flakes considering all the hints. Or he wants to find out that the hints are contradictory and the roommate lied to him, that is, no box has the flakes.

Input

The first line contains two integers n and m (1 ≤ n ≤ 1000, 0 ≤ m ≤ 1000) which represent the number of boxes and the number of hints correspondingly. Next m lines contain hints like "To the left of i" and "To the right of i", where i is integer (1 ≤ i ≤ n). The hints may coincide.

Output

The answer should contain exactly one integer — the number of boxes that should necessarily be checked or "-1" if the hints are contradictory.

Examples

Input

2 1
To the left of 2


Output

1


Input

3 2
To the right of 1
To the right of 2


Output

1


Input

3 1
To the left of 3


Output

2


Input

3 2
To the left of 2
To the right of 1


Output

-1

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
template <class T>
void splitstr(const string &s, vector<T> &out) {
  istringstream in(s);
  out.clear();
  copy(istream_iterator<T>(in), istream_iterator<T>(), back_inserter(out));
}
template <class T>
T readValue(string s) {
  T result;
  istringstream sin(s);
  sin >> result;
  return result;
}
template <class T>
void initArray(T *arr, int size, T value) {
  for (int i = 0; i < size; i++) arr[i] = value;
}
template <class T>
inline T gcd(T a, T b) {
  return (!a) ? b : gcd(b % a, a);
}
template <class T>
inline T mod(T a, T p) {
  a %= p;
  return (a < 0) ? a + p : a;
}
template <class T>
inline int num_bits(T n) {
  return (!n) ? 0 : 1 + numbits(n & (n - 1));
}
template <class T>
inline T inverse(T a, T m) {
  a = mod<T>(a, m);
  return (a == 1) ? 1 : mod((1 - m * inverse(m % a, a)) / a, m);
}
template <class T>
inline bool is_prime(T a) {
  T lim = (T)sqrt((double)a);
  for (T i = 2; i <= T(lim + 1E-9); i++)
    if (a % i == 0) return false;
  return true;
}
template <class T>
inline T power(T a, T p, T mod) {
  if (!p) return 1;
  T temp = power(a, p >> 1, mod);
  temp = (temp * temp) % mod;
  if (p & 1) temp = (temp * a) % mod;
  return temp;
}
void get_primes(int start, int end, vector<int> &vi) {
  int *p = new int[end + 1];
  initArray<int>(p, end + 1, 0);
  p[1] = 1;
  for (int i = 2; i <= end; i++) {
    if (!p[i]) {
      if (i >= start) vi.push_back(i);
      for (int j = 2 * i; j <= end; j += i) p[j] = 1;
    }
  }
  delete[] p;
}
bool dfs(int current, int final, int total, int *visited, int **edges,
         bool flow) {
  if (current == final) return true;
  if (visited[current]) return false;
  visited[current] = true;
  for (int i = 0; i < total; i++)
    if (edges[current][i] && dfs(i, final, total, visited, edges, flow)) {
      if (flow) {
        edges[current][i]--;
        edges[i][current]++;
      }
      return true;
    }
  return false;
}
int flow(int in, int out, int total, int **edges) {
  int result = 0;
  int *visited = new int[total];
  while (initArray<int>(visited, total, 0),
         dfs(in, out, total, visited, edges, true))
    result++;
  delete[] visited;
  return result;
}
void create_set(int x, int *P, int *rank) {
  P[x] = x;
  rank[x] = 0;
}
int find_set(int x, int *P) {
  if (x != P[x]) P[x] = find_set(P[x], P);
  return P[x];
}
bool merge_sets(int x, int y, int *P, int *rank) {
  int Px = find_set(x, P);
  int Py = find_set(y, P);
  if (Px == Py) return false;
  if (rank[Px] > rank[Py])
    P[Py] = Px;
  else
    P[Px] = Py;
  if (rank[Px] == rank[Py]) rank[Py]++;
  return true;
}
template <typename T>
int read_cum_freq(int index, T *tree) {
  int sum = 0;
  while (index) {
    sum += tree[index];
    index -= (index & -index);
  }
  return sum;
}
template <typename T>
void upd_freq(int index, int mxIndex, int value, T *tree) {
  while (index <= mxIndex) {
    tree[index] += value;
    index += (index & -index);
  }
}
template <typename T>
int read_freq(int index, T *tree) {
  return read_cum_freq(index, tree) - read_cum_freq(index - 1, tree);
}
void build_failure_function(const string &str, int *temp_arr) {
  temp_arr[0] = temp_arr[1] = 0;
  for (int i = 2; i <= ((int)(str).size()); i++) {
    temp_arr[i] = -1;
    for (int ind = temp_arr[i - 1]; temp_arr[i] == -1; ind = temp_arr[ind]) {
      if (str[ind] == str[i - 1]) {
        temp_arr[i] = ind + 1;
      } else if (ind == 0) {
        temp_arr[i] = 0;
      }
    }
  }
}
void KMP(const string &text, const string &pattern, int *res) {
  int *temp_arr = new int[((int)(pattern).size()) + 1];
  build_failure_function(pattern, temp_arr);
  int i = 0;
  int ind = 0;
  while (i < ((int)(text).size())) {
    if (text[i] == pattern[ind]) {
      res[i] = ++ind;
      if (res[i] == ((int)(pattern).size())) {
        ind = temp_arr[ind];
      }
      i++;
    } else if (ind == 0) {
      res[i++] = 0;
    } else {
      ind = temp_arr[ind];
    }
  }
  delete[] temp_arr;
}
void setup(int value, string name) {
  string name_in = name + ".in";
  string name_out = name + ".out";
  freopen(name_in.c_str(), "r", stdin);
  if (value) {
    freopen(name_out.c_str(), "w", stdout);
  }
}
bool arr[1001];
int main() {
  int n;
  std::cin >> n;
  int m;
  std::cin >> m;
  cin.get();
  memset(arr, 0, sizeof(arr));
  for (int j = 0; j < m; j++) {
    string str;
    getline(cin, str);
    int val = atoi(str.substr(str.find("of") + 3).c_str()) - 1;
    if (str.find("left") != string::npos) {
      for (int i = val; i < 1001; i++) arr[i] = true;
    } else {
      for (int i = 0; i <= val; i++) arr[i] = true;
    }
  }
  int res = 0;
  for (int i = 0; i < n; i++)
    if (!arr[i]) res++;
  if (res)
    std::cout << res << std::endl;
  else
    std::cout << -1 << std::endl;
  return 0;
}

```