#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
using namespace std;

/*BigInteger
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/rational.hpp>
namespace xxx = boost::multiprecision;
using Bint = xxx::cpp_int;
using Real = xxx::number<xxx::cpp_dec_float<1024>>;
*/

#define int long long
#define pb(x) push_back(x)
#define m0(x) memset((x), 0, sizeof(x))
#define mm(x) memset((x), -1, sizeof(x))

//container
#define ALL(x) (x).begin(), (x).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EACH(i, c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define UNIQUE(v) (v).erase(unique((v).begin(), (v).end()), (v).end());
#define PERM(c) \
  sort(ALL(c)); \
  for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))

// debug
#define GET_VAR_NAME(variable) #variable
#define test(x) cout << GET_VAR_NAME(x) << " = " << x << endl;

// bit_macro
#define bit(n) (1LL << (n))
#define bitset(a, b) (a) |= (1 << (b))
#define bitunset(a, b) (a) &= ~(1 << (b))
#define bitcheck(a, b) ((((a) >> (b)) & 1) == 1)
#define bitcount(a) __builtin_popcountll((a))

//typedef
typedef long long lint;
typedef unsigned long long ull;
typedef complex<long double> Complex;
typedef pair<int, int> P;
typedef tuple<int, int, int> TP;
typedef vector<int> vec;
typedef vector<vec> mat;

//constant
constexpr int INF = (int)1e18;
constexpr int MOD = (int)1e9 + 7;
constexpr double PI = (double)acos(-1);
constexpr double EPS = (double)1e-10;
constexpr int dx[] = {-1, 0, 0, 1, 0, -1, -1, 1, 1};
constexpr int dy[] = {0, -1, 1, 0, 0, 1, -1, 1, -1};

//
template <typename T>
void chmax(T &a, T b) { a = max(a, b); }
template <typename T>
void chmin(T &a, T b) { a = min(a, b); }
//
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T>
inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}

//
struct Accelerate_Cin {
  Accelerate_Cin() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(20);
  };
};

//O(N^2)
//Garnerのアルゴリズム
//中国剰余定理

inline int mod(int a, int m) {
  int res = a % m;
  if (res < 0) res += m;
  return res;
}

int GCD(int a, int b) {
  if (b == 0)
    return a;
  else
    return GCD(b, a % b);
}

int extGCD(int a, int b, int &p, int &q) {
  if (b == 0) {
    p = 1;
    q = 0;
    return a;
  }
  int d = extGCD(b, a % b, q, p);
  q -= a / b * p;
  return d;
}

int modinv(int a, int m) {
  int x, y;
  extGCD(a, m, x, y);
  return mod(x, m);
}

int PreGarner(vector<int> &b, vector<int> &m, int MOD) {
  int res = 1;
  for (int i = 0; i < (int)b.size(); ++i) {
    for (int j = 0; j < i; ++j) {
      int g = GCD(m[i], m[j]);
      if ((b[i] - b[j]) % g != 0) return -1;

      m[i] /= g;
      m[j] /= g;
      int gi = GCD(m[i], g), gj = g / gi;

      do {
        g = GCD(gi, gj);
        gi *= g, gj /= g;
      } while (g != 1);

      m[i] *= gi, m[j] *= gj;
      b[i] %= m[i], b[j] %= m[j];
    }
  }

  for (int i = 0; i < (int)b.size(); ++i) (res *= m[i]) %= MOD;
  return res;
}

int Garner(vector<int> b, vector<int> m, int MOD) {
  m.push_back(MOD);
  vector<int> coeffs((int)m.size(), 1);
  vector<int> constants((int)m.size(), 0);
  //m同士で互いに素でない場合があるとき。
  //preGarner(b,m,MOD);
  for (int k = 0; k < (int)b.size(); ++k) {
    int t = mod((b[k] - constants[k]) * modinv(coeffs[k], m[k]), m[k]);
    for (int i = k + 1; i < (int)m.size(); ++i) {
      (constants[i] += t * coeffs[i]) %= m[i];
      (coeffs[i] *= m[k]) %= m[i];
    }
  }
  return constants.back();
}

signed main() {
  int N;
  cin >> N;
  vec X(N), Y(N);

  bool flag = true;
  for (int i = 0; i < N; i++) {
    cin >> X[i] >> Y[i];
    if (X[i]) flag = false;
  }

  int lcm = PreGarner(X, Y, MOD);
  if (lcm == -1) {
    cout << -1 << endl;
    return 0;
  }
  if (flag) {
    cout << lcm << endl;
    return 0;
  }

  cout << Garner(X, Y, MOD) << endl;
  return 0;
}