// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
int main() {
    // Input
    int A, B, C, D, E;
    cin >> A >> B >> C >> D >> E;

    // Calculation
    int p[10'009];
    p[0] = 0;
    p[1] = D;
    for (int i = 2; i < 10'009; ++i) {
        if (i % 10) p[i] = p[i-1];
        else if (E <= p[i-1]) p[i] = p[i-1] - E;
        else p[i] = p[i-1];
    }

    // Output
    int ans = 0;
    for (int i = 1; i <= A*(B-C); ++i) ans += p[i];
    cout << ans << endl;
}