#include<bits/stdc++.h>
#define maxN 1000005
#define INF 0x3f3f3f3f
using namespace std;
int n,k,d,ind;
int v[maxN],dp[maxN];
int main()
{
    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]);
    sort(v+1,v+n+1);
    dp[0]=0;
    for(int i=1;i<=n;i++) dp[i]=INF;
    ind=0;
    for(int i=1;i<=n;i++)
    {
        while(v[i]-v[ind]>=(d-1)) ind++;
        dp[i]=min(dp[i-1]+1,dp[ind-1]+k);
    }
    printf("%d\n",dp[n]);
    return 0;
}