#include <iostream>

using namespace std;

int main()
{
    int green, red, n, wait = 0, child;
    cin >> green >> red >> n;

    for (int i = 0; i < n; i++) {
        cin >> child;
        if (((child % (green + red)) - green) >= 0) {
            wait += red - ((child % (green + red)) - green);
        }
    }
    cout << wait;

    return 0;
}