#include <iostream>
#include <fstream>
#define NMAX 1000000

using namespace std;

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

int d, n, k, v[NMAX+10], st[NMAX+10], dp[NMAX+10];

int main()
{
    fin >> d >> n >> k;
    for(int i=1; i<=n; i++)
        fin >> v[i];
    int curr = 1;
    for(int i=1; i<=n; i++){
        while(v[curr] + d - 1 <= v[i])
            curr++;
        st[i] = curr;
    }
    dp[1] = 1;
    for(int i=2; i<=n; i++)
        dp[i] = min(dp[i-1] + 1, dp[st[i]-1] + k);
    fout << dp[n] << '\n';
    return 0;
}