#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10, inf = 1e8;
int s, l, a[maxn], g[maxn], dp[maxn], n, p1, p2, p3;
deque<int> mn, mx, mn2;
int main() {
  cin >> n >> s >> l;
  p1 = p2 = p3 = 1;
  mn2.push_back(--p3);
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    while (mx.size() && a[mx.back()] <= a[i]) mx.pop_back();
    while (mn.size() && a[mn.back()] >= a[i]) mn.pop_back();
    mn.push_back(i);
    mx.push_back(i);
    while (a[mx.front()] - a[mn.front()] > s) {
      if (p1 == mx.front()) mx.pop_front();
      if (p1 == mn.front()) mn.pop_front();
      p1++;
    }
    g[i] = p1;
    while (p2 <= i - l) {
      while (mn2.size() && dp[mn2.back()] >= dp[p2]) mn2.pop_back();
      mn2.push_back(p2++);
    }
    while (p3 < min(g[i] - 1, i - l))
      if (p3++ == mn2.front()) mn2.pop_front();
    dp[i] = dp[mn2.front()] + 1;
    if (i - l + 1 < g[i]) dp[i] = inf;
  }
  cout << (dp[n] >= inf ? -1 : dp[n]) << endl;
  return 0;
}
