#include <bits/stdc++.h>
using namespace std;

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

	int a = A * (B  - C);
	int ans = 0;
	int X = 0;
	for( int i = 1; i <= a; i++ ) {
		if( i == 1 ) {
			X = D;
			ans = X;
		}
		else {
			if( i % 10 ) ans += X;
			else {
				if( X < E ) ans += X;
				else {
					X -= E;
					ans += X;
				}
			}
		}
	}

	cout << ans << endl;
}