#include "bits/stdc++.h"

using namespace std;

#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl

typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
template<class S, class T> pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first + t.first, s.second + t.second); }
template<class S, class T> pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template<class S, class T> ostream& operator<<(ostream& os, pair<S, T> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
#define fi first
#define se second
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define rep1(i,n) for(ll i=1;i<=(ll)(n);i++)
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define rrep1(i,n) for(ll i=(ll)(n);i>0;i--)
#define REP(i,a,b) for(ll i=(ll)a;i<(ll)b;i++)
#define in(x, a, b) (a <= x && x < b)
#define all(v) v.begin(),v.end()
#define UNIQUE(v) v.erase(unique(all(v)), v.end())
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; }
const ll inf = 1000000001;
const ll INF = 2e18;
const ll MOD = 1000000007;
const double pi = 3.14159265358979323846;
#define Sp(p) cout<<setprecision(15)<< fixed<<p<<endl;
int dx[4] = { 1,0, -1,0 }, dy[4] = { 0,1,0,-1 };
int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
#define fio() cin.tie(0); ios::sync_with_stdio(false);



//ax + by = gcd(a, b) となるx, yをもとめる
ll extgcd(ll a, ll b, ll& x, ll& y) {
	ll d = a;
	if (b != 0) {
		d = extgcd(b, a%b, y, x);
		y -= (a / b)*x;
	}
	else {
		x = 1; y = 0;
	}
	return d;
}

//中国剰余定理
//am[i].first:a_i, am[i].second:m_i
//return (x, y) y = lcm(m1, m2, ..., m_n),  x%m_i = a_i
typedef __int128 lll;
pll crt(vector<pll> am) {
	rep(i, am.size() - 1) {
		ll g, x, y, z;
		am[i].first = (am[i].first % am[i].second + am[i].second) % am[i].second;
		am[i + 1].first = (am[i + 1].first % am[i + 1].second + am[i + 1].second) % am[i + 1].second;
		g = extgcd(am[i].second, am[i + 1].second, x, y);
		if (am[i].first%g != am[i].second%g) return pll(-1, 0); //解なし
		lll lcm = (lll)am[i].second*(am[i + 1].second / g);
		if (lcm < am[i].second) return pll(-2, 0); //オーバーフロー
		ll mo = am[i + 1].second = am[i].second * am[i + 1].second;
		lll v = am[i].first + ((lll)(am[i].second / g) * x % mo * (am[i + 1].first - am[i].first + mo) % mo);
		am[i + 1].first = (v%mo + mo) % mo;
	}
	return am.back();
}


int main() {
	int n;
	cin >> n;
	vector<pll> am(n);
	rep(i, n) {
		cin >> am[i].first >> am[i].second;
	}
	auto ans = crt(am);
	cout << ans.first % MOD << endl;
}