#include <bits/stdc++.h>
#define FastIO (cin.tie(0), cout.tie(0), ios::sync_with_stdio(false))
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;

void solve() {
  int a, b, c, d, e;
  cin >> a >> b >> c >> d >> e;

  int total = 0;
  int X = d;

  for (int ame = 1; ame <= a * (b - c); ame++) {
    if (ame != 1 && ame % 10 == 0 && X - e >= 0) X -= e;
    total += X;
  }
  cout << total << '\n';
}

int main() {
  FastIO;
  solve();
  return 0;
}