#include <bits/stdc++.h>

#define mp(_,__) make_pair(_,__)

using namespace std;

int T,n,m;

int a[],b[];

pair <int,int> a1,a2,b1,b2;

pair <pair<int,int>,pair<int,int> > A,B;

int main(){

    scanf("%d",&T);

    while(T--)

    {

        scanf("%d%d",&n,&m);

        memset(a,0x3f,sizeof(a));

        memset(b,0x3f,sizeof(b));

        for (int i = ;i < n;++i) scanf("%d",a+i);

        for (int i = ;i < m;++i) scanf("%d",b+i);

        a1 = mp(a[]+,0x3f3f3f3f),b1 = mp(b[]+,0x3f3f3f3f);

        a[]++;b[]++;

        if (a[] > a[]) swap(a[],a[]);

        if (b[] > b[]) swap(b[],b[]);

        a2 = mp(a[],a[]),b2 = mp(b[],b[]);

        if (a1 > a2) swap(a1,a2);

        if (b1 > b2) swap(b1,b2);

        A = make_pair(a1,a2),B = make_pair(b1,b2);

        if ( A == B) puts("");

        else if (A > B) puts("-1");

        else puts("");

    }

    return ;

}