#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<cstring>
using namespace std;
#define ll long long
#define in(a) a=read()
#define out(a) printf("%d\n",a)
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define FORD(i,a,b) for(int i=a;i>=b;i--)
#define FORL(i,x) for(int i=head[x];i;i=nxt[i])
#define clr(a,x) memset(a,x,sizeof(a))
inline ll read(){
    char c=getchar();ll f=1,x=0;
    while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}
    while(c>='0'&&c<='9')x=x*10+(c-'0'),c=getchar();
    return x*f;
}
#define mod 1000000007
void MOD(int &x){x-=x>=mod?mod:0;}
#define maxn 500010
#define inf (1<<30)

int main(){
    #ifndef ONLINE_JUDGE
    freopen("1.in","r",stdin);
    #endif
    int t;
    in(t);
    while(t--){
        int a,b;
        in(a);in(b);
        if(a<b)swap(a,b);
        int x=a-b;
        if(!x&&a>1){
            printf("%d %d\n",2,a);
            continue;
        }
        int pos=x;
        for(int i=2;i*i<=x;i++)
            if(x%i==0){
                pos=i;
                break;
            }
        if(pos>1)printf("%d %d\n",pos,x);
        else printf("%d %d\n",-1,-1);
    }
}