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

long long mod_inv(long long a, long long mod) {
  if (mod == 1) return 0;
  a %= mod;
  long long b = mod, s = 1, t = 0;
  while (1) {
    if (a == 1) return s;
    t -= (b / a) * s;
    b %= a;
    if (b == 1) return t + mod;
    s -= (a / b) * t;
    a %= b;
  }
}

pair<long long, long long> extgcd(long long a, long long b) {
  long long s = a, t = b;
  long long xs = 1, ys = 0, xt = 0, yt = 1;
  while (t > 0) {
    long long u = s / t;
    s -= t * u;
    xs -= xt * u;
    ys -= yt * u;
    swap(s, t);
    swap(xs, xt), swap(ys, yt);
  }
  return {xs, ys};
}

pair<long long, long long> garner(vector<long long> Rem, vector<long long> Mod) {
  assert (Rem.size() == Mod.size());
  int n = int(Mod.size());
  // garner
  long long x = 0, prod = 1;
  for (int i = 0; i < n; i++) {
    if (Mod[i] == 1) continue;
    long long g = gcd(prod, Mod[i]);
    long long c = (Rem[i] + (Mod[i] - x % Mod[i])) % Mod[i];
    if (c % g) return {-1, -1}; // not exist
    long long m = Mod[i] / g;
    c = (c / g) * mod_inv((prod / g) % m, m) % m;
    x = x + c * prod;
    prod *= m;
    x %= prod;
  }
  return {x, prod};
}

long long garner2(vector<long long> Rem, vector<long long> Mod, long long mod) {
  assert (Rem.size() == Mod.size());
  int n = int(Mod.size());
  // garner
  vector<long long> C(n);
  for (int i = 0; i < n; i++) {
    long long x = 0, prod = 1;
    for (int j = 0; j < i; j++) {
      x = (x + C[j] * prod % Mod[i]) % Mod[i];
      prod = (prod * Mod[j]) % Mod[i];
    }
    long long g = gcd(prod, Mod[i]);
    long long c = (Rem[i] + (Mod[i] - x)) % Mod[i];
    if (c % g) return -1; // not exist
    long long m = Mod[i] / g;
    c = (c / g) * mod_inv((prod / g) % m, m) % m;
    Mod[i] /= g, C[i] = c;
  }
  long long ans = 0;
  for (int i = n - 1; i >= 0; i--) ans = ((ans * Mod[i]) % mod + C[i]) % mod;
  return ans;
}

void solve() {
  int N;
  cin >> N;
  vector<long long> X, Y;
  for (int i = 0; i < N; i++) {
    long long x, y;
    cin >> x >> y;
    X.push_back(x), Y.push_back(y);
  }
  cout << garner2(X, Y, 1000000007) << endl;
}

int main() {
  int T = 1;
  //cin >> T;
  for (int t = 0; t < T; t++) solve();
}