b.cpp

#include <bits/stdc++.h>
using namespace std;
//
#define ll long long
#define ull unsigned long long
#define pb push_back
#define mx 100010
#define mod 1000000007
#define inf INT_MAX
#define pi acos(-1)
#define endl '\n'
#define fin freopen("input", "r", stdin)
#define Fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
//
#define MAX 10000000
vector<ll> v;
set<ll> se, se1;

void sieve()
{
    vector<bool> isprime(MAX, 1);
    for (int i = 3; i * i <= MAX; i += 2)
    {
        if (isprime[i])
        {
            for (int j = i * i; j <= MAX; j += i + i)
            {
                isprime[j] = false;
            }
        }
    }
    v.push_back(2);
    for (int i = 3; i <= MAX; i += 2)
    {
        if (isprime[i])
        {
            v.push_back(i);
        }
    }
}

void prime_fac(ll n, ll m) {
    vector<ll>::iterator it;
    for (it = v.begin(); it != v.end(); it++)
    {
        if (n % *it == 0 || m % *it == 0)
        {
            se.insert(*it);
            while (n % *it == 0 || m % *it == 0)
            {
                if (n % *it == 0) n /= *it;
                if (m % *it == 0) m /= *it;
            }
        }
    }
    if (n != 1) se.insert(n);
    if (m != 1) se.insert(m);
}

int main() {
    sieve();
    ll t, a, b, x;
    cin >> t;

    set<ll>::iterator it;

    ll val = -1;
    vector<ll> res(MAX, 0);

    for (ll i = 0; i < t; i++) {
        scanf("%lld %lld", &a, &b);
        if (i == 0) prime_fac(a, b);
        else {
            ll cnt = 0;
            for (it = se.begin(); it != se.end(); it++) {
                if (*it > max(a, b)) break;
                if (a % *it == 0 || b % *it == 0) {
                    res[cnt] += 1;
                    if (res[cnt] == t - 1) { val = *it; break; }
                }
                cnt++;
            }
        }
    }

    if (t == 1) val = *se.begin();
    cout << val << endl;
}