#include <iostream>
#include <cassert>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int a, b, c, d, e; cin >> a >> b >> c >> d >> e;
  int x = b - c;
  if (x <= 0) {
    cout << 0 << endl;
    return 0;
  }

  int cur = d;
  int ans = 0;
  for (int i = 1; i <= x * a; i++) {
    if (i % 10 != 0) {
      ans += cur;
    } else if (e <= cur) {
      cur -= e;
      ans += cur;
    } else {
      ans += cur;
    }
  }
  cout << ans << endl;
  return 0;
}