#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;
using ll = long long;
int main() {
  int a, b, c, d, e;
  cin >> a >> b >> c >> d >> e;
  int ans = 0;
  int x = d;
  for(int i = 0; i < a * (b - c); i++) {
    if((i + 1) % 10 == 0 && x >= e) {
      x -= e;
    }
    ans += x;
  }
  cout << ans << endl;
  return 0;
}