#include <cstdio>
#include <algorithm>
#define Nmax 1000005

using namespace std;

int D,N,K,v[Nmax],dp[Nmax];

int main()
{
    int i,j=1;
    freopen ("zombie.in","r",stdin);
    freopen ("zombie.out","w",stdout);
    scanf("%d%d%d", &D,&N,&K);
    for(i=1;i<=N;++i)
        scanf("%d", &v[i]);
    for(i=1;i<=N;++i)
    {
        while(v[i]-v[j]>=D-1)
            ++j;
        dp[i]=min(dp[i-1]+1,dp[j-1]+K);
    }
    printf("%d\n", dp[N]);
    return 0;
}