#include<bits/stdc++.h>
typedef long long ll;
using namespace std;

ll gcd(ll a, ll b) {
	return !b ? a : gcd(b, a%b);
}

bool check(ll x) {
	if(x <= 10) return false;
	string s1 = "";
	while(x) {
		s1 += x%10 + '0';
		x /= 10;
	}
	reverse(s1.begin(), s1.end());
	int n = s1.length();
	string s2 = s1.substr(0, (n+1)/2);
	string s3 = s1.substr((n+1)/2);
	ll a = 0, b = 0;
	for(int i=0; i<s2.length(); ++i)
		a = a*10 + s2[i] - '0';
	for(int i=0; i<s3.length(); ++i)
		b = b*10 + s3[i] - '0';
	return gcd(a, b) == 1;
}

int main() {
	ll a, b, c;
	int t; scanf("%d", &t);
	while(t--) {
		scanf("%lld%lld", &a, &b);
		c = -1;
		for(ll i=b; i>=a; --i) {
			if(check(i)) {
				c = i;
				break;
			}
		}
		printf("%lld\n", c);
	}
	return 0;
}