#include <bits/stdc++.h>
#define MAXN 1000000

using namespace std;

ifstream fin  ("zombie.in");
ofstream fout ("zombie.out");

int dp[MAXN+5], v[MAXN+5], poz[MAXN+5];
int d, n, k, p;

int main(){
    fin>>d>>n>>k; p=1;
    for(int i=1; i<=n; i++){
        fin>>v[i];

        while(v[p] + d < v[i])
            p++;

        poz[i]=p;
    }
    dp[1]=1;
    for(int i=2; i<=n; i++)
        dp[i] = min(dp[i-1]+1, dp[poz[i]-1]+k);
    fout<<dp[n];
    return 0;
}