#include <bits/stdc++.h>
using namespace std;

int main() {
    int A, B, C, D, E;
    cin >> A >> B >> C >> D >> E;
    int a = A * (B - C);
    int answer = 0;
    
    for (int i = 1; i <= a; i++) {
        answer += max(D - E * (i / 10), D % E);
    }
    cout << answer << endl;
}