#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
//#include <atcoder/all>
using namespace std;
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define repl(i, a) for (long long i = (long long)0; i < (long long)a; ++i)
#define rrep(i, a) for (int i = (int)a; i > -1; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define REPL(i, a, b) for (long long i = (long long)a; i < (long long)b; ++i)
#define RREP(i, a, b) for (int i = (int)a; i > b; --i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
#define popcountll __builtin_popcountll
#define fi first
#define se second
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll mod_998244353 = 998244353;
constexpr ll INF = 1LL << 60;

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

//using lll = boost::multiprecision::cpp_int;
template <class T>
inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

template <class T>
inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

ll mypow(ll x, ll n, const ll &p = -1) {  // x^nをmodで割った余り

  if (p != -1) {
    x = (x % p + p) % p;
  }
  ll ret = 1;
  while (n > 0) {
    if (n & 1) {
      if (p != -1)
        ret = (ret * x) % p;
      else
        ret *= x;
    }
    if (p != -1)
      x = (x * x) % p;
    else
      x *= x;
    n >>= 1;
  }
  return ret;
}

template <typename T>
struct myrand {
  random_device seed;
  mt19937 mt;
  myrand() : mt(seed()) {}
  T operator()(T a, T b) {  //[a,b)
    uniform_int_distribution<T> dist(a, b - 1);
    return dist(mt);
  }
};

//using namespace atcoder;

//------------------------
//------------------------
//------------------------
//------------------------
//------------------------

template<typename T=ll>
T extgcd(T a,T b,T &x,T &y){
  T d=a;
  if(b==0){
    x=1,y=0;
  }else{
    d=extgcd(b,a%b,y,x);
    y-=a/b*x;
  }
  return d;
}

template<typename T=ll>
T modinv(T a,T m){
  T x,y;
  if(extgcd(a,m,x,y)==1){
    return (x%m+m)%m;
  }
  return -1;//no inv
}

template<typename T=ll>
T preGarner(vector<T> &r,vector<T> &m,T MOD=-1){
  assert(r.size()==m.size());
  T LCM=1;
  int n=r.size();
  for(int i=0;i<n;++i){
    for(int j=i+1;j<n;++j){
      T g=gcd<T,T>(m[i],m[j]);
      if((r[i]-r[j])%g!=0)return -1;

      m[i]/=g;
      m[j]/=g;

      T gi=gcd<ll,ll>(m[i],g),gj=g/gi;

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

      m[i]*=gi,m[j]*=gj;

      r[i]%=m[i],r[j]%=m[j];
    }
  }
  for(int i=0;i<n;++i){
    LCM*=m[i];
    if(MOD!=-1){
      LCM%=MOD;
    }
  }
  return LCM;
}
template<typename T=ll>
pair<T,T> CRT_Garner(vector<T> &r,vector<T> &m,T MOD=-1){
  assert(r.size()==m.size());
  T LCM=preGarner(r,m,MOD);
  if(LCM==-1){
    return make_pair(0,0);
  }

  T prod_m=1,prod_t=0;
  int n=r.size();

  for(int i=0;i<n;++i){
    T t_k=(r[i]-prod_t)*modinv(prod_m,m[i]);
    t_k=(t_k%m[i]+m[i])%m[i];
    //cout<<t_k<<"\n";
    prod_t+=t_k*prod_m;
    prod_m*=m[i];
    
    if(MOD!=-1){
      prod_t%=MOD;
      prod_m%=MOD;
    }
  }
  return make_pair(prod_t,LCM);
}

void solve() {
  int n;
  cin>>n;
  vector<ll>r(n),m(n);
  rep(i,n){
    cin>>r[i]>>m[i];
  }
  auto [R,M]=CRT_Garner(r,m,mod);
  cout<<(M==0?-1:(R==0?M:R))<<"\n";
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}