#include<stdio.h>
#include<algorithm>
using namespace std;
int v[1000005];
int main()
{
    int D,N,K;
    freopen("zombie.in","r",stdin);
    freopen("zombie.out","w",stdout);
    scanf("%d%d%d",&D,&N,&K);
    for(int i=1;i<=N;++i)
        scanf("%d",&v[i]);
    long long sol=0;
    for(int i=1;i<=N;++i){
        int j=v[i],aux=i;
        for( ; i<=N && v[i]-j<=D ; i++ );
        sol+=min(K,i-aux);
    }
    printf("%lld",sol);
    fclose(stdin);fclose(stdout);
    return 0;
}