#include<stdio.h>
int main()
{
	int u,j,n,m,q,p,w;
	while(scanf("%d",&n),n)
	{
		double l;
	  double  min=344443443.0;
		while(n--)
		{
			scanf("%d%d",&q,&w);

			if(w>=0)
			{
				l=w*1.00+4.5*3600*1.0/q;
				if(min>l) min=l;
			}
		}
		p=min;
	if(min-p!=0)
		printf("%.f\n",min+0.5);
		else printf("%d\n",p);
	}
}