#include<iostream>
#include<math.h>
using namespace std;
int main() {
	int need, pencle, price,spend,max=99999;
	cin >> need;

	for (int i = 1;i < 4;i++)
	{
		cin >> pencle >> price;
		if ((need, pencle, price) > 10000 && (need, pencle, price) < 1)
		{
			exit(1);
		}
	
		if (need%pencle == 0)
		{
			spend = need / pencle * price;
		}
		else  
		{
			spend = (need / pencle+1) * price;
		}
		if (max > spend)
		{
			max = spend;
		}
	}
	cout << max << endl;

	
	
	system("pause");
	return 0;
}