#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h> 
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

void lena_sort_util (unsigned int len, unsigned int comp)
{
    
    
}

int main(){
    int q; 
    scanf("%d",&q);
    for(int a0 = 0; a0 < q; a0++){
        int len; 
        int c; 
        scanf("%d %d",&len,&c);
        if (len == 1 && c == 0)
            printf ("1\n");
        else if (len == 1 && c != 0)
            printf ("-1\n");
        else 
            lena_sort_util (len, c);
    }
    return 0;
}