#include <bits/stdc++.h>
using namespace std;
#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

inline int power(int a, int b, int mod=M) {
    int x = 1;
    a %= mod;
    while (b) {
        if (b & 1) x = (x * a) % mod; 
        a = (a * a) % mod;
        b >>= 1;
    }
    return x;
}


//_ ***************************** START Below *******************************




vector<int> a;

int consistency1(int n, int k, int m){
	
	vector<int> dp(n+1, INF);
	dp[0] = 0;
	
	
	for(int i=1; i<=n; i++){
		
		int j = i-1;
		int maxi = a[i-1];
		int mini = a[i-1];
		
		while(j>=0){
			if(i-j >= k){
				if(maxi - mini <= m)	dp[i] = min(dp[i], dp[j] + 1);
			}
			
			if(j-1>=0){
				maxi = max(maxi, a[j-1]);
				mini = min(mini, a[j-1]);
			}
			j--;
		}
	}
	
	return dp[n] == INF ? -1 : dp[n];
}















int practice(int n, int k, int m){


    return 0;
}





void solve() {
    
    int n, k, m;
    cin>> n >> k >> m;
    
    a.resize(n);
    for(int i=0; i<n; i++) cin >> a[i];
    
    cout << consistency1(n, k, m) << endl;


}





int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}