/* -*- coding: utf-8 -*-
 *
 * 1453.cc:  No.1453 手助け - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  int a, b, c, d, e;
  scanf("%d%d%d%d%d", &a, &b, &c, &d, &e);

  int n = a * (b - c);
  int sum = 0;

  for (int i = 1, x = d; i <= n; i++) {
    if (i % 10 == 0 && e <= x) x -= e;
    sum += x;
  }

  printf("%d\n", sum);
  return 0;
}