#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vpi = vector<pair<int, int>>;
using pi = pair<int, int>;
const int nax = 1e5 + 7;
const int mod = 1e9 + 7;
const int inf = numeric_limits<int>::max() - (int)9e6;
struct monotonic_queue {
  queue<int> qu;
  deque<int> mx, mn;
  void push(int v) {
    qu.push(v);
    while (mx.size() && mx.back() < v) mx.pop_back();
    mx.push_back(v);
    while (mn.size() && mn.back() > v) mn.pop_back();
    mn.push_back(v);
  }
  void pop() {
    if (mx.front() == qu.front()) mx.pop_front();
    if (mn.front() == qu.front()) mn.pop_front();
    qu.pop();
  }
  int front() const { return qu.front(); }
  int max() const { return mx.front(); }
  int min() const { return mn.front(); }
  int size() const { return qu.size(); }
  bool empty() { return qu.empty(); }
};
int n;
void test() {
  cin >> n;
  int s, l;
  cin >> s >> l;
  vi v(n);
  for (int i = 0; i < (int)n; i++) cin >> v[i];
  monotonic_queue q;
  vi g(n, n);
  for (int i = n - 1, j = n - 1; i >= 0; i--) {
    while (j >= 0 and (q.empty() or (((q.max() - q.min()) <= s)))) {
      q.push(v[j--]);
    }
    g[i] = (((q.max() - q.min()) <= s) ? j : j + 1);
    if (((int)(q).size())) q.pop();
  }
  while (((int)(q).size())) q.pop();
  vi dp(n + 1, inf);
  dp[0] = 0;
  for (int i = l, j = 0; i <= n; i++) {
    q.push(dp[i - l]);
    while (((int)(q).size()) and j <= g[i - 1]) q.pop(), j++;
    if (((int)(q).size())) dp[i] = q.min() + 1;
  }
  cout << (dp[n] >= inf ? -1 : dp[n]);
}
signed main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  int T = 1;
  while (T--) {
    test();
    cout << "\n";
  }
  return 0;
}
