#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
	int x;
	int a[3],b[3],c[4],wxy=0,temp;
	c[4]=99999999;
	cin>>x;
	for(int i=1;i<=3;i++){
		cin>>a[i]>>b[i];
		c[i]=0;
		for(int j=1;wxy<x;j++){
			wxy+=a[i];
			c[i]+=b[i];
		}
		wxy=0;
	}
	for(int j=1;j<=3;j++){
	    for(int i=1;i<=3;i++){
		    if(c[i]>c[i+1]){
		    temp=c[i+1];
			c[i+1]=c[i];
			c[i]=temp;
		    }
	    }
	}
	cout<<c[1]<<endl;
	return 0;
}