#include <iostream>
using namespace std;

int main() {
	// your code goes here
	int a,b,c,d,e;
	cin >> a >> b >> c >> d >> e;
	int count=0;
	for(int i=1;i<a*(b-c)+1;i++){
		if(i%10==0){
			if(e<=d){
				d=d-e;
			}
		}
		count=count+d;
	}
	cout << count;
	return 0;
}