#include <iostream>
#include <vector>
#include <stdio.h>

using namespace std;

int main() {
	int A, B, C, D, E;
	cin >> A >> B >> C >> D >> E;

	int num = A * (B - C);

	int step = num / 10;

	long long ans = 0;
	for (int i = 0; i < step; i++) {
		ans += max(10 * (D - E * i), 10*(D%E));
	}

	ans += (num % 10) * max((D - E * step), D % E);

	cout << ans << endl;
}