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

/// --- modulo Library {{{ ///
ll extgcd(ll a, ll b, ll& x, ll& y) {
  if(b==0) {
    x = 1; y = 0;
    return a;
  }
  ll d = extgcd(b, a % b, y, x);
  y -= (a / b) * x;
  return d;
}
ll modpow(ll a, ll b, ll mod = 1e9 + 7) {
  a = (a % mod + mod) % mod;
  ll r = 1;
  while(b){
    if(b & 1) r = r * a % mod;
    a = a * a % mod;
    b >>= 1;
  }
  return r;
}
ll modinv(ll a, ll mod = 1e9 + 7) {
  a = (a % mod + mod) % mod;
  ll x = 0, y = 0;
  extgcd(a, mod, x, y);
  return (x % mod + mod) % mod;
}
/// }}}--- ///

// require mods library
/// Garner Library {{{ ///
ll garner(vector<ll> n, vector<ll> mods, ll mod){
  n.emplace_back(0);
  mods.emplace_back(mod);
  vector<ll> coeffs(n.size(), 1); // v_i の係数
  vector<ll> constants(n.size(), 0); // v_i の項より後ろの項の和,答え mod mods[i]
  for(int i = 0; i < (int) n.size(); i++) {
    // coeffs[i] * v_i + constants[i] == n[i] (mod mods[i]) を解く
    ll v = (n[i] - constants[i]) * modinv(coeffs[i], mods[i]) % mods[i];
    if (v < 0) v += mods[i];
    for (int j = i + 1; j < (int) n.size(); j++) {
      (constants[j] += coeffs[i] * v) %= mods[j];
      (coeffs[j] *= mods[i]) %= mods[j];
    }
  }
  return constants.back();
}
/// }}}--- ///

int main() {
  ios::sync_with_stdio(false), cin.tie(0);
  int n; cin >> n;
  vector<ll> vs(n), ms(n);
  for(int i = 0; i < n; i++) {
    cin >> vs[i] >> ms[i];
  }

  vector<int> primes;
  for(int i = 2; (ll) i*i <= 1e9; i++) {
    int flag = 1;
    for(int x : primes) if(i % x == 0) {
      flag = 0; break;
    }
    if(flag) primes.emplace_back(i);
  }

  for(int m : ms) {
    for(int p : primes) while(m % p == 0) m /= p;
    if(m != 1) primes.emplace_back(m);
  }

  for(int p : primes) {
    vector< pair<int, int> > ps;
    for(int i = 0; i < n; i++) {
      if(ms[i] % p == 0) {
        int lg = 0;
        while(ms[i] % p == 0) ms[i] /= p, lg++;
        ps.emplace_back(lg, i);
      }
    }
    if(ps.size() < 1) continue;
    sort(begin(ps), end(ps));
    int base = vs[ps.back().second];
    for(auto d : ps) {
      if(vs[d.second] % p != base % p) {
        cout << -1 << endl;
        return 0;
      }
      if(d.second == ps.back().second) {
        for(int i = 0; i < d.first; i++) ms[d.second] *= p;
      }
    }
  }

  for(int i = 0; i < n; i++) vs[i] = vs[i] % ms[i];

  cout << garner(vs, ms, 1e9 + 7) << endl;
}