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

int main(){
  int A, B, C, D, E;
  cin >> A >> B >> C >> D >> E;
  
  int ans = D, X = D;
  for(int i = 2; i <= A * (B - C); i++){
    if(i % 10 == 0 && E <= X) X -= E;
    ans += X;
  }
  
  cout << ans;
}