#include<stdio.h>
int main()
{
   long n,max=9999999;
   static int a[3];
   static int b[3];
   static int m[3];
   scanf("%d", &n);
   scanf("%d%d", &a[1], &b[1]);
   scanf("%d%d", &a[2], &b[2]);
   scanf("%d%d", &a[3], &b[3]);
   if (n % a[1] == 0)
   {
   	m[1] = n / a[1] * b[1];
   }
   else
   {
   	m[1] = (n / a[1] + 1) * b[1];
   }
   if (n % a[2] == 0)
   {
   	m[2] = n / a[2] * b[2];
   }
   else
   {
   	m[2] = (n / a[2] + 1) * b[2];
   }
   if (n % a[3] == 0)
   {
   	m[3] = n / a[3] * b[3];
   }
   else
   {
   	m[3] = (n / a[3] + 1) * b[3];
   }
   if (m[1] <= min)
   {
   	min = m[1];
   }
   if (m[2] <= min)
   {
   	min = m[2];
   }
   if (m[3] <= min)
   {
   	min = m[3];
   }
   printf("%d\n", min);
}

a数组是铅笔数量 b数组是铅笔价钱 m数组是每一组所需要花的钱