#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int a, b, c, d, e;
  cin >> a >> b >> c >> d >> e;
  int cnt = a * (b - c);
  int sum = 0, prev = d;
  for (int i = 1; i <= cnt; i++) {
    if (i % 10 != 0) {
      sum += prev;
    }
    else {
      if (e <= prev) {
        sum += (prev -= e);
      }
      else {
        sum += prev;
      }
    }
  }
  cout << sum << endl;
  return 0;
}