#include <cmath>
using namespace std;
int main()
{
	double a,b,a1,b1,a2,b2;
	long long c1,c2,c3;
	int n;
	cin>>n;
	cin>>a>>b;
	cin>>a1>>b1;
	cin>>a2>>b2;
	c1+=(ceil(n/a))*b;
	c2+=(ceil(n/a1))*b1;
	c3+=(ceil(n/a2))*b2;
	if(c1<c2&&c1<c3)
	{
		cout<<(ceil(n/a))*b;
	}
	else if(c2<c1&&c2<c3)
	{
		cout<<(ceil(n/a1))*b1;
	}
	else
	{
		cout<<(ceil(n/a2))*b2;
	}
	return 0;
}