#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#include <bitset>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

template<typename T>T gcd(T x, T y){if(y==0)return x;else return gcd(y,x%y);}
template<typename T>T lcm(T x, T y){ return x == 0 ? 0 : x/gcd(x,y)*y; }


vector<bool> isprime;
vector<int> primes;
void sieve(int n){
	if((int)isprime.size() >= n+1) return;
	isprime.assign(n+1, true);
	isprime[0] = isprime[1] = false;
	int sqrtn = (int)(sqrt(n * 1.) + .5);
	for(int i = 2; i <= sqrtn; i ++) if(isprime[i]) {
		for(int j = i * i; j <= n; j += i)
			isprime[j] = false;
	}
	primes.clear();
	for(int i = 2; i <= n; i ++) if(isprime[i])
		primes.push_back(i);
}

typedef int FactorsInt;
typedef vector<pair<FactorsInt,int> > Factors;
void primeFactors(FactorsInt x, Factors &out_v) {
	out_v.clear();
	int sqrtx = (int)(sqrt(x*1.) + 10.5);
	sieve(sqrtx);
	for(vector<int>::const_iterator p = primes.begin(); p != primes.end(); ++ p) {
		if(*p > sqrtx) break;
		if(x % *p == 0) {
			int t = 1;
			x /= *p;
			while(x % *p == 0) {
				t ++;
				x /= *p;
			}
			out_v.push_back(make_pair(*p, t));
		}
	}
	if(x != 1) out_v.push_back(make_pair(x, 1));
}

long long inverse(signed long long a, const long long MOD) {
	a %= MOD;
	if(a < 0) a += MOD;
	signed long long b = MOD, u = 1, v = 0;
	while(b) {
		signed long long t = a / b;
		a -= t * b; swap(a, b);
		u -= t * v; swap(u, v);
	}
	if(u < 0) u += MOD;
	return u;
}

ll crt(ll a1, ll a2, ll n1, ll n2) {
	ll b = n1 % n2;
	ll t = inverse(b, n2);
	ll h = ((a2 - a1) * t % n2 + n2) % n2;
	return a1 + n1 * h;
}

int powpq(int p, int q) {
	int r = 1;
	rep(i, q) r *= p;
	return r;
}

int main() {
	sieve(31623);
	int N;
	scanf("%d", &N);
	Factors fs;
	map<int,pii> mods;
	bool ok = true;
	rep(i, N) {
		int X, Y;
		cin >> X >> Y;
		primeFactors(Y, fs);
		each(j, fs) {
			int p = j->first, q = j->second;
			int pq = powpq(p, q);
			pii &t = mods[p];
			int u = min(pq, powpq(p, t.first));
			ok &= t.second % u == X % u;
			if(t.first < q) {
				t.first = q;
				t.second = X % pq;
			}
		}
	}
	if(!ok) {
		puts("-1");
		return 0;
	}
	
	ll a = 0, n = 1;
	each(i, mods) {
		int p = i->first, q = i->second.first, x = i->second.second;
		int pq = powpq(p, q);
		a = crt(a, x, n, pq);
		n *= pq;
	}
	if(a == 0)
		a += n;
	printf("%lld\n", a);
	return 0;
}