#include <bits/stdc++.h> 

using namespace std;

typedef long long ll;

const int N = (int)1e6 + 12;

const ll inf = 11e17;

ll b, p, d, n, a[N];
ll dp[N];
void test() {
    cin >> b >> p >> d >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    for(int i = 1; i <= n; i++) {
        dp[i] = inf;
        for(int j = i - 1; j >= 0; j--) {
            ll r = (a[i] - a[j] - 1);
            if(a[j] % p < a[i] % p) {
                dp[i] = min(dp[i], dp[j] + (a[i] / p) * d - (a[j] / p) * d + p - ((a[i] % p) - (a[j] % p)));
            }
            else dp[i] = min(dp[i], dp[j] +(a[i] / p) * d - (a[j] / p) * d - d + a[j] % p - a[i] % p);
        }
    }
    ll res = inf;
    for(int i = 0; i <= n; i++) {
        ll r = b - a[i] - 1;
        res = min(res, dp[i] + (r / p)  * d);
    }
    cout << res + b << '\n';
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int t = 1;
    // cin >> t;

    while(t--) 
        test();

    return 0;
}