#include <cstdio>
#include <cstring>
#include <algorithm>
#define maxN 1000002
using namespace std;
int v[maxN], i, j, d, n, k, pos, dp[maxN];
void read()
{
    freopen("zombie.in", "r", stdin);
    scanf("%d %d %d", &d, &n, &k);
    pos = 1;
    for (i = 1; i <= n; ++ i)
    {
        scanf("%d", &v[i]);
        while (pos < i && v[i] - v[pos] >= d)
            ++ pos;
        dp[i] = min(dp[i - 1] + 1, dp[pos - 1] + k);
    }
}
void write()
{
    freopen("zombie.out", "w", stdout);
    printf("%d\n", dp[n]);
}
int main()
{
    read();
    write();
    return 0;
}