#include<iostream>
#include<iomanip>
#include<bitset>
#include<algorithm>
#include<string>
#include<vector>
#include<cstdio>
#include<cmath>
#include<queue>
#include<map>
#include<set>
using namespace std;
using ll=long long;

int main(){
    int A, B, C, D, E;
    cin >> A >> B >> C >> D >> E;
    int np = A * (B - C) * D;
    int discount = (A * (B - C) / 10 - (E - 1) / 10) * E;
    cout << np - discount << endl;
    return 0;
}