#include <bits/stdc++.h>

using namespace std;

int main() {
    int a, b, c, d, e;
    cin >> a >> b >> c >> d >> e;

    if (b-c == 0) {
        puts("0");
        return 0;
    }

    int ans = d;
    int pre = d;
    for (int i = 1; i < (b-c)*a; i++) {
        if ((i+1)%10 == 0 && e <= pre) {
            pre = pre-e;
        }
        ans += pre;
    }

    cout << ans << endl;

    return 0;
}