#include<stdio.h> 
#include<math.h>
void main(){
    int N,a,b;
    double time;
    scanf("%d",&N);
    while(N!=0){
        int min=0;
        for(int i=1;i<=N;i++){
            scanf("%d %d",&a,&b);
            if(b>=0)
                time=(double)4500*3.6/a+b;
            if(min==0||min>time)
                min=(int)ceil(time);
        }
        printf("%d\n",min);
        scanf("%d",&N);
    }
}