#include <cstdio>
#include<iostream>
#include<algorithm>
using namespace std;
int d,n,k,i,j,t[1000005],stg[1000005];
int main()
{
    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",&t[i]);
    stg[1]=1;
    for(i=1,j=2;j<=n;)
    {
        if(t[j]-t[i]>=d){i++;continue;}
        stg[j]=i;j++;
    }
    for(i=1;i<=n;i++)
        t[i]=min(t[i-1]+1,t[stg[i]-1]+k);
    printf("%d\n",t[n]);
    return 0;
}