#include <bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(c) (c).begin(),(c).end()
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
#define MINF(a) memset(a,0x3f,sizeof(a))
#define POW(n) (1LL<<(n))
#define IN(i,a,b) (a <= i && i <= b)
using namespace std;
template <typename T> inline bool CHMIN(T& a,T b) { if(a>b) { a=b; return 1; } return 0; }
template <typename T> inline bool CHMAX(T& a,T b) { if(a<b) { a=b; return 1; } return 0; }
template <typename T> inline void SORT(T& a) { sort(ALL(a)); }
template <typename T> inline void REV(T& a) { reverse(ALL(a)); }
template <typename T> inline void UNI(T& a) { sort(ALL(a)); a.erase(unique(ALL(a)),a.end()); }
const int MOD = 1000000007;
const int INF = 0x3f3f3f3f3f3f3f3f;
const double EPS = 1e-10;
/* ---------------------------------------------------------------------------------------------------- */

map<int,int> prime_factor(int x) {
  map<int,int> res;
  for (int i = 2; i*i <= x; i++) {
    while (x % i == 0) {
      res[i]++;
      x /= i;
    }
  }
  if (x != 1) res[x]++;
  return res;
}

// 拡張gcd
int ext_gcd(int a, int b, int &x, int &y) {
  if (b == 0) {
    x = 1; y = 0; return a;
  }
  int q = a/b;
  int g = ext_gcd(b,a-q*b,x,y);
  int z = x-q*y;
  x = y; y = z;
  return g;
}

// 逆元 | a と m は互いに素
int inv_mod(int a, int m) {
  int x,y;
  ext_gcd(a,m,x,y);
  x %= m;
  if (x < 0) x += m;
  return x;
}

// garner のアルゴリズム | (m_i,m_j) は互いに素
int garner(vector<int> r, vector<int> m) {
  int n = r.size();
  int x = r[0]%m[0];
  int mul = m[0];
  for (int i = 1; i < n; i++) {
    int t = (r[i]-x)*inv_mod(mul,m[i])%m[i];
    if (t < 0) t += m[i];
    (x += t*mul) %= MOD;
    (mul *= m[i]) %= MOD;
  }
  return x;
}

signed main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(10);

  int N;
  cin >> N;
  map<int,int> mp,mx;
  REP(i,N) {
    int X,Y;
    cin >> X >> Y;
    map<int,int> pf = prime_factor(Y);
    for (auto p : pf) {
      int mul = 1;
      for (int j = 0; j < p.second; j++) {
        mul *= p.first;
        if (mp.count(mul)) {
          if (mp[mul] != X%mul) {
            cout << -1 << endl;
            return 0;
          }
        }
        mp[mul] = X%mul;
        CHMAX(mx[p.first],mul);
      }
    }
  }
  vector<int> r,m;
  for (auto p : mx) {
    r.push_back(mp[p.second]);
    m.push_back(p.second);
  }
  cout << garner(r,m) << endl;

  return 0;
}