#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;

int main(){
    int a, b, c, d, e, t, r, sum1;
    cin >> a >> b >> c >> d >> e;
    t = (b -c)*a;
    r = t/10;
    for (int i = 1; i <= t; i++){
        if (i%10) sum1 += d;
        else if (d > e){
            d = d-e;
            sum1 += d;
        } else sum1 += d;
    }
    cout << sum1 << endl;
}