#include <bits/stdc++.h> 

using namespace std;

typedef long long ll;

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

const ll inf = (ll)1e18;
#define  int ll

ll dp[2100][2100], b, p, d, n, a[N];
ll get(ll l, ll r) {
    return r / p - max(0ll, (l - 1)) / p;
}
void test() {
    cin >> b >> p >> d >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    n++;
    a[n] = b;
    for(int i = 1; i <= n; i++) {
        for(int j = 0; j < 2100; j++) {
            dp[i][j] = inf;
        }
    }
    ll res = inf;
    for(int i = 1; i <= n; i++) {
        for(int j = (a[i] - a[i - 1]); j < 2100; j++) {
            ll prv = j - (a[i] - a[i - 1]);
            if(dp[i - 1][prv] == inf) continue;
            dp[i][j] = min(dp[i][j], dp[i - 1][prv] + get(prv + 1, j - 1) * d);
            res = min(res, dp[n][j] + j);
        }
        for(int j = 1; j < 2100; j++) {
            dp[i][j] = min(dp[i][j], dp[i][j - 1]);
        }
    }
    cout << res << '\n';
}


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

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

    while(t--) 
        test();

    return 0;
}