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

int main() {
  int a, b, c, d, e;
  cin >> a >> b >> c >> d >> e;
  
  int num = a * (b - c);
  
  vector<int> x(num + 1);
  x.at(1) = d;
  int ans = d;
  for (int i = 2; i <= num; i++) {
    if (i % 10 != 0) x.at(i) = x.at(i - 1);
    else {
      if (e <= x.at(i - 1)) x.at(i) = x.at(i - 1) - e;
      else x.at(i) = x.at(i - 1);
    }
    ans += x.at(i);
  }
  
  cout << ans << '\n';
}