#include <bits/stdc++.h>
const double pi = 3.141592653589793238462643383279;
namespace MyMinMax {
template <typename T>
inline T mn(const T x, const T y) {
  return x < y ? x : y;
}
template <typename T>
inline T mx(const T x, const T y) {
  return x > y ? x : y;
}
template <typename T>
inline bool chmin(T &x, const T y) {
  return (x > y) && ((x = y), 1);
}
template <typename T>
inline bool chmax(T &x, const T y) {
  return (x < y) && ((x = y), 1);
}
template <typename T, typename... Args>
inline T mx(const T x, const Args... args) {
  return mx(x, mx(args...));
}
template <typename T, typename... Args>
inline T mn(const T x, const Args... args) {
  return mn(x, mn(args...));
}
}  // namespace MyMinMax
using namespace MyMinMax;
namespace IO {
const int DPAIRSIZ = 1 << 18;
char BB[DPAIRSIZ], *SS = BB, *TT = BB;
inline char getcha() {
  return SS == TT && (TT = (SS = BB) + fread(BB, 1, DPAIRSIZ, stdin), SS == TT)
             ? EOF
             : *SS++;
}
template <typename T = int>
inline T read() {
  T x = 0;
  int fu = 1;
  char c = getcha();
  while (c > 57 || c < 48) {
    if (c == 45) fu = -1;
    c = getcha();
  }
  while (c <= 57 && c >= 48) {
    x = x * 10 + c - 48;
    c = getcha();
  }
  x *= fu;
  return x;
}
template <typename T>
inline void read(T &x) {
  x = 0;
  int fu = 1;
  char c = getcha();
  while (c > 57 || c < 48) {
    if (c == 45) fu = -1;
    c = getcha();
  }
  while (c <= 57 && c >= 48) {
    x = x * 10 + c - 48;
    c = getcha();
  }
  x *= fu;
}
template <typename T>
inline void read(T *bg, T *ed) {
  while (bg != ed) read(*bg++);
}
inline void read(char &ch) {
  ch = getcha();
  while (ch <= 32) ch = getcha();
}
inline void read(char *s) {
  char ch = getcha();
  while (ch <= 32) ch = getcha();
  while (ch > 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
inline void sread(char *s) {
  char ch = getcha();
  while (ch < 32) ch = getcha();
  while (ch >= 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
inline void pread(char *&s) {
  char ch = getcha();
  while (ch <= 32) ch = getcha();
  while (ch > 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
inline void spread(char *&s) {
  char ch = getcha();
  while (ch < 32) ch = getcha();
  while (ch >= 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
template <typename T, typename... Args>
inline void read(T &x, Args &...args) {
  read(x);
  read(args...);
}
char out[DPAIRSIZ], *Out = out;
inline void putcha(char x) {
  *Out++ = x;
  if (Out - out >= (DPAIRSIZ)) fwrite(out, 1, Out - out, stdout), Out = out;
}
template <typename T>
inline void fprint(T x) {
  if (x < 0) putcha(45), x = -x;
  if (x > 9) fprint(x / 10);
  putcha(x % 10 + 48);
}
inline void print() { putcha(10); }
template <typename T>
inline void print(T x) {
  fprint(x);
  putcha(10);
}
inline void print(char *ch) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
}
inline void put(char *ch) {
  while (*ch != '\0') putcha(*(ch++));
}
inline void print(const char *ch) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
}
inline void put(const char *ch) {
  while (*ch != '\0') putcha(*(ch++));
}
template <typename T, typename... Args>
inline void print(T x, Args... args) {
  fprint(x);
  putcha(32);
  print(args...);
}
template <typename... Args>
inline void print(const char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(32);
  print(args...);
}
template <typename... Args>
inline void print(char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(32);
  print(args...);
}
template <typename T, typename... Args>
inline void printl(T x, Args... args) {
  fprint(x);
  putcha(10);
  printl(args...);
}
template <typename... Args>
inline void printl(const char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
  printl(args...);
}
template <typename... Args>
inline void printl(char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
  printl(args...);
}
template <typename T>
inline void sprint(T x) {
  fprint(x);
  putcha(32);
}
template <typename T, typename... Args>
inline void sprint(T x, Args... args) {
  fprint(x);
  putcha(32);
  sprint(args...);
}
template <typename T>
inline void sprint(T *bg, T *ed) {
  while (bg != ed) sprint(*bg++);
}
template <typename T>
inline void print(T *bg, T *ed) {
  while (bg != ed) sprint(*bg++);
  putcha(10);
}
template <typename T>
inline void printl(T *bg, T *ed) {
  while (bg != ed) print(*bg++);
}
class AutoFlush {
 public:
  ~AutoFlush() { fwrite(out, 1, Out - out, stdout); }
} __AutoFlush;
}  // namespace IO
using namespace IO;
const int INF = 0x3f3f3f3f;
const long long INFll = 0x3f3f3f3f3f3f3f3fll;
const int MAXN = 1e5 + 5;
int n, m, q, a[MAXN];
std ::multiset<int> s;
int b[MAXN];
int t[MAXN << 2];
inline void pushup(int rt) { t[rt] = mn(t[rt << 1], t[rt << 1 | 1]); }
void build(int rt, int l, int r) {
  t[rt] = INF;
  if (l == r) return;
  int mid = (l + r) >> 1;
  build(rt << 1, l, mid);
  build(rt << 1 | 1, mid + 1, r);
}
void modify(int rt, int l, int r, int x, int y) {
  chmin(t[rt], y);
  if (l == r) return;
  int mid = (l + r) >> 1;
  x <= mid ? modify(rt << 1, l, mid, x, y)
           : modify(rt << 1 | 1, mid + 1, r, x, y);
}
int query(int rt, int l, int r, int x, int y) {
  if (x <= l && r <= y) return t[rt];
  int mid = (l + r) >> 1;
  if (x > mid) return query(rt << 1 | 1, mid + 1, r, x, y);
  if (y <= mid) return query(rt << 1, l, mid, x, y);
  return mn(query(rt << 1, l, mid, x, y), query(rt << 1 | 1, mid + 1, r, x, y));
}
signed main() {
  read(n, q, m);
  read(a + 1, a + n + 1);
  int r = 0;
  for (int l = (1); l <= (n); ++l) {
    while (r <= n && (s.empty() || *(--s.end()) - *s.begin() <= q))
      s.emplace(a[++r]);
    b[l] = r;
    auto it = s.find(a[l]);
    s.erase(it);
  }
  build(1, 1, n + 1);
  modify(1, 1, n + 1, n + 1, 0);
  for (int i = (n); i >= (1); --i) {
    if (i + m > b[i]) continue;
    const int res = query(1, 1, n + 1, i + m, b[i]);
    if (res == INF) continue;
    modify(1, 1, n + 1, i, res + 1);
  }
  const int ans = query(1, 1, n + 1, 1, 1);
  print(ans == INF ? -1 : ans);
}

### Prompt

Please provide a cpp coded solution to the problem described below:

Alexandra has a paper strip with n numbers on it. Let's call them ai from left to right.

Now Alexandra wants to split it into some pieces (possibly 1). For each piece of strip, it must satisfy:

  * Each piece should contain at least l numbers.
  * The difference between the maximal and the minimal number on the piece should be at most s.



Please help Alexandra to find the minimal number of pieces meeting the condition above.

Input

The first line contains three space-separated integers n, s, l (1 ≤ n ≤ 105, 0 ≤ s ≤ 109, 1 ≤ l ≤ 105).

The second line contains n integers ai separated by spaces ( - 109 ≤ ai ≤ 109).

Output

Output the minimal number of strip pieces.

If there are no ways to split the strip, output -1.

Examples

Input

7 2 2
1 3 1 2 4 1 2


Output

3


Input

7 2 2
1 100 1 100 1 100 1


Output

-1

Note

For the first sample, we can split the strip into 3 pieces: [1, 3, 1], [2, 4], [1, 2].

For the second sample, we can't let 1 and 100 be on the same piece, so no solution exists.

### Response

```cpp
#include <bits/stdc++.h>
const double pi = 3.141592653589793238462643383279;
namespace MyMinMax {
template <typename T>
inline T mn(const T x, const T y) {
  return x < y ? x : y;
}
template <typename T>
inline T mx(const T x, const T y) {
  return x > y ? x : y;
}
template <typename T>
inline bool chmin(T &x, const T y) {
  return (x > y) && ((x = y), 1);
}
template <typename T>
inline bool chmax(T &x, const T y) {
  return (x < y) && ((x = y), 1);
}
template <typename T, typename... Args>
inline T mx(const T x, const Args... args) {
  return mx(x, mx(args...));
}
template <typename T, typename... Args>
inline T mn(const T x, const Args... args) {
  return mn(x, mn(args...));
}
}  // namespace MyMinMax
using namespace MyMinMax;
namespace IO {
const int DPAIRSIZ = 1 << 18;
char BB[DPAIRSIZ], *SS = BB, *TT = BB;
inline char getcha() {
  return SS == TT && (TT = (SS = BB) + fread(BB, 1, DPAIRSIZ, stdin), SS == TT)
             ? EOF
             : *SS++;
}
template <typename T = int>
inline T read() {
  T x = 0;
  int fu = 1;
  char c = getcha();
  while (c > 57 || c < 48) {
    if (c == 45) fu = -1;
    c = getcha();
  }
  while (c <= 57 && c >= 48) {
    x = x * 10 + c - 48;
    c = getcha();
  }
  x *= fu;
  return x;
}
template <typename T>
inline void read(T &x) {
  x = 0;
  int fu = 1;
  char c = getcha();
  while (c > 57 || c < 48) {
    if (c == 45) fu = -1;
    c = getcha();
  }
  while (c <= 57 && c >= 48) {
    x = x * 10 + c - 48;
    c = getcha();
  }
  x *= fu;
}
template <typename T>
inline void read(T *bg, T *ed) {
  while (bg != ed) read(*bg++);
}
inline void read(char &ch) {
  ch = getcha();
  while (ch <= 32) ch = getcha();
}
inline void read(char *s) {
  char ch = getcha();
  while (ch <= 32) ch = getcha();
  while (ch > 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
inline void sread(char *s) {
  char ch = getcha();
  while (ch < 32) ch = getcha();
  while (ch >= 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
inline void pread(char *&s) {
  char ch = getcha();
  while (ch <= 32) ch = getcha();
  while (ch > 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
inline void spread(char *&s) {
  char ch = getcha();
  while (ch < 32) ch = getcha();
  while (ch >= 32) *s++ = ch, ch = getcha();
  *s = '\0';
}
template <typename T, typename... Args>
inline void read(T &x, Args &...args) {
  read(x);
  read(args...);
}
char out[DPAIRSIZ], *Out = out;
inline void putcha(char x) {
  *Out++ = x;
  if (Out - out >= (DPAIRSIZ)) fwrite(out, 1, Out - out, stdout), Out = out;
}
template <typename T>
inline void fprint(T x) {
  if (x < 0) putcha(45), x = -x;
  if (x > 9) fprint(x / 10);
  putcha(x % 10 + 48);
}
inline void print() { putcha(10); }
template <typename T>
inline void print(T x) {
  fprint(x);
  putcha(10);
}
inline void print(char *ch) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
}
inline void put(char *ch) {
  while (*ch != '\0') putcha(*(ch++));
}
inline void print(const char *ch) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
}
inline void put(const char *ch) {
  while (*ch != '\0') putcha(*(ch++));
}
template <typename T, typename... Args>
inline void print(T x, Args... args) {
  fprint(x);
  putcha(32);
  print(args...);
}
template <typename... Args>
inline void print(const char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(32);
  print(args...);
}
template <typename... Args>
inline void print(char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(32);
  print(args...);
}
template <typename T, typename... Args>
inline void printl(T x, Args... args) {
  fprint(x);
  putcha(10);
  printl(args...);
}
template <typename... Args>
inline void printl(const char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
  printl(args...);
}
template <typename... Args>
inline void printl(char *ch, Args... args) {
  while (*ch != '\0') putcha(*(ch++));
  putcha(10);
  printl(args...);
}
template <typename T>
inline void sprint(T x) {
  fprint(x);
  putcha(32);
}
template <typename T, typename... Args>
inline void sprint(T x, Args... args) {
  fprint(x);
  putcha(32);
  sprint(args...);
}
template <typename T>
inline void sprint(T *bg, T *ed) {
  while (bg != ed) sprint(*bg++);
}
template <typename T>
inline void print(T *bg, T *ed) {
  while (bg != ed) sprint(*bg++);
  putcha(10);
}
template <typename T>
inline void printl(T *bg, T *ed) {
  while (bg != ed) print(*bg++);
}
class AutoFlush {
 public:
  ~AutoFlush() { fwrite(out, 1, Out - out, stdout); }
} __AutoFlush;
}  // namespace IO
using namespace IO;
const int INF = 0x3f3f3f3f;
const long long INFll = 0x3f3f3f3f3f3f3f3fll;
const int MAXN = 1e5 + 5;
int n, m, q, a[MAXN];
std ::multiset<int> s;
int b[MAXN];
int t[MAXN << 2];
inline void pushup(int rt) { t[rt] = mn(t[rt << 1], t[rt << 1 | 1]); }
void build(int rt, int l, int r) {
  t[rt] = INF;
  if (l == r) return;
  int mid = (l + r) >> 1;
  build(rt << 1, l, mid);
  build(rt << 1 | 1, mid + 1, r);
}
void modify(int rt, int l, int r, int x, int y) {
  chmin(t[rt], y);
  if (l == r) return;
  int mid = (l + r) >> 1;
  x <= mid ? modify(rt << 1, l, mid, x, y)
           : modify(rt << 1 | 1, mid + 1, r, x, y);
}
int query(int rt, int l, int r, int x, int y) {
  if (x <= l && r <= y) return t[rt];
  int mid = (l + r) >> 1;
  if (x > mid) return query(rt << 1 | 1, mid + 1, r, x, y);
  if (y <= mid) return query(rt << 1, l, mid, x, y);
  return mn(query(rt << 1, l, mid, x, y), query(rt << 1 | 1, mid + 1, r, x, y));
}
signed main() {
  read(n, q, m);
  read(a + 1, a + n + 1);
  int r = 0;
  for (int l = (1); l <= (n); ++l) {
    while (r <= n && (s.empty() || *(--s.end()) - *s.begin() <= q))
      s.emplace(a[++r]);
    b[l] = r;
    auto it = s.find(a[l]);
    s.erase(it);
  }
  build(1, 1, n + 1);
  modify(1, 1, n + 1, n + 1, 0);
  for (int i = (n); i >= (1); --i) {
    if (i + m > b[i]) continue;
    const int res = query(1, 1, n + 1, i + m, b[i]);
    if (res == INF) continue;
    modify(1, 1, n + 1, i, res + 1);
  }
  const int ans = query(1, 1, n + 1, 1, 1);
  print(ans == INF ? -1 : ans);
}

```