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

int main() {
  int A, B, C, D, E; cin >> A >> B >> C >> D >> E;
  int ame = A*(B-C), ans = 0, last = 0;
  for(int i = 1; i <= ame; i++){
    if(i == 1){
      ans += D;
      last = D;
    }
    else{
      if(i%10 == 0 and E <= last) last -= E;
      ans += last;
    }
  }
  cout << ans << endl;
}