#include <cstdio>
#include <algorithm>

using namespace std;

#define maxn 1000010

int d, n, k, p1;
int v[maxn], dp[maxn];

int main()
{
    freopen("zombie.in", "r", stdin);
    freopen("zombie.out", "w", stdout);

    scanf("%d%d%d", &d, &n, &k);
    p1=1;
    for(int i=1; i<=n; ++i)
    {
        scanf("%d", &v[i]);
        while(v[i]-v[p1]>=d)
            ++p1;
        dp[i]=min(dp[i-1]+1, dp[p1-1]+k);
    }

    printf("%d\n", dp[n]);
    return 0;
}