#include<stdio.h>
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        if(x==1||y==1)
        {
            printf("-1\n");
        }
        else if(x!=17&&y!=17)
        {
            printf("17\n");
        }
        else
        {
            printf("13\n");
        }
    }

}