#include<bits/stdc++.h>
using namespace std;
using u64 = uint_least64_t;
using s64 = int_least64_t;
using ll = uint_least64_t;

int main(){
	int a,b,c,d,e;
	cin >> a >> b >> c >> d >> e;
	
	int friend_num  = b - c;
	int candy_num = a * friend_num;
	if (candy_num == 0){
		cout << '0' << endl;
		return 0;
	}
	if (candy_num == 1){
		cout << d << endl;
		return 0;
	}
	int x = d;
	int price = x;
	for (int i = 2; i <= candy_num; ++i){
		if (i % 10 != 0){
			price += x;
		}
		else{
			if (i % 10 == 0){
				if (e <= x){
					x -= e;
					price += x;
				}
				else{
					price += x;
				}
			}
		}
	}
	cout << price << endl;
	return 0;
}