#include<bits/stdc++.h>

using namespace std;
using ll=long long;
#define rep2(i, a, n) for(int i = (a); i < (n); i++)
#define rep(i, n) rep2(i,0,n)

int main() {
    int A, B, C, D, E;
    cin >> A >> B >> C >> D >> E;
    int a = A * (B - C);
    int answer = 0;
    
    rep2(i,1,a+1){
        answer += max(D - E * (i / 10), D % E);
    }
    cout << answer << endl;
}