#include<cstdio>
int vis[5000005];

void preWork(int n){
    vis[1] = 1;
    for(int i = 2; i <= n; i++){
        if(!vis[i]){
            for(int j = 2*i; j <= n; j+=i) vis[j] = 1;
        }
    }
}

int main(){
    preWork(5000000);
    int T;
    scanf("%d",&T);
    while(T--){
        long long a,p;
        scanf("%lld%lld",&a,&p);
        if(vis[p]) printf("-1\n");
        else printf("1\n"); 
    }
    return 0;
}