#include <bits/stdc++.h>
using namespace std;
bool dbg = 0;
void bad(string mes = "Impossible") {
  cout << mes;
  exit(0);
}
void bad(int mes) {
  cout << mes;
  exit(0);
}
template <typename T>
string bin(T x, int st = 2) {
  string ans = "";
  while (x > 0) {
    ans += char('0' + x % st);
    x /= st;
  }
  reverse(ans.begin(), ans.end());
  return ans.empty() ? "0" : ans;
}
template <typename T>
void amax(T& x, T y) {
  x = max(x, y);
}
template <typename T>
void amin(T& x, T y) {
  x = min(x, y);
}
template <typename T>
T input() {
  T ans = 0, m = 1;
  char c = ' ';
  while (!((c >= '0' && c <= '9') || c == '-')) {
    c = getchar();
  }
  if (c == '-') m = -1, c = getchar();
  while (c >= '0' && c <= '9') {
    ans = ans * 10 + (c - '0'), c = getchar();
  }
  return ans * m;
}
template <typename T>
void read(T& a) {
  a = input<T>();
}
template <typename T>
void read(T& a, T& b) {
  read(a), read(b);
}
template <typename T>
void read(T& a, T& b, T& c) {
  read(a, b), read(c);
}
template <typename T>
void read(T& a, T& b, T& c, T& d) {
  read(a, b), read(c, d);
}
const int inf = 2e9 + 20;
const long double eps = 1e-12;
const int maxn = 1e5 + 12, base = 1e9 + 7;
const long long llinf = 4e18 + 5;
template <typename T>
T binpow(T n, T second) {
  if (second <= 0) return 1LL;
  if (second % 2 == 0) {
    T b = binpow(n, second / 2);
    return (1LL * b * b) % base;
  } else {
    return (1LL * binpow(n, second - 1) * n) % base;
  }
}
int a[maxn];
int tree[4 * maxn];
void update(int v, int tl, int tr, int pos, int val) {
  if (tl == tr)
    tree[v] = val;
  else {
    int m = (tl + tr) >> 1;
    if (pos <= m)
      update(v << 1, tl, m, pos, val);
    else
      update(v << 1 | 1, m + 1, tr, pos, val);
    tree[v] = min(tree[v << 1], tree[v << 1 | 1]);
  }
}
int get(int v, int tl, int tr, int l, int r) {
  if (l > r) return inf;
  if (tl == l && tr == r) return tree[v];
  int m = (tl + tr) >> 1;
  return min(get(v << 1, tl, m, l, min(r, m)),
             get(v << 1 | 1, m + 1, tr, max(l, m + 1), r));
}
multiset<int> st;
int cur() {
  if (st.empty()) return -1;
  return *st.rbegin() - *st.begin();
}
int main() {
  int n, second, l;
  read(n, second, l);
  for (int i = 0; i < n; i++) {
    read(a[i]);
  }
  if (l > n) bad(-1);
  for (int i = 0; i + 1 < l; i++) {
    st.insert(a[i]);
    update(1, 0, n - 1, i, inf);
  }
  if (cur() > second) bad(-1);
  int L = 0;
  for (int i = l - 1; i < n; i++) {
    st.insert(a[i]);
    while (cur() > second) {
      st.erase(st.find(a[L]));
      L++;
    }
    if (i - l < L - 1) {
      update(1, 0, n - 1, i, inf);
      continue;
    }
    if (L == 0) {
      update(1, 0, n - 1, i, 1);
      continue;
    }
    int cur = get(1, 0, n - 1, L - 1, i - l) + 1;
    update(1, 0, n - 1, i, cur);
  }
  int ans = get(1, 0, n - 1, n - 1, n - 1);
  if (ans == inf) ans = -1;
  cout << ans;
  return 0;
}
