#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y-1);(X) >=0;--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<class T> using vv=vector<vector<T>>;
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"{"; rep(i,t.size()) {os<<t[i]<<",";} os<<"}"<<endl; return os;}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}

const ll MOD=1e9+7;

ll modpow(ll r,ll n,ll m=MOD){
  ll re=1,d=r%m;
  for(;n;n/=2){
    if(n&1)(re*=d)%=m;
    (d*=d)%=m;
  }
  return re;
}

const int PRIME_MAX=1123456;
vector<int> primes;
int prime[PRIME_MAX];
void findPrime(){
  for(int i=2;i<PRIME_MAX;i++)if(!prime[i]){
      primes.pb(i);
      for(int j=i*2;j<PRIME_MAX;j+=i)
	prime[j]=1;
  }
}
//extGCD
ll extgcd(ll a,ll b,ll &x,ll &y){
  ll g=a; x=1,y=0;
  if(b){
    g=extgcd(b,a%b,y,x);
    y-=(a/b)*x;
  }
  return g;
}

//m[i]=p[i]^t : 逆元求める用 modpow書き換える
ll garner(vector<ll> a,vector<ll> m,vector<ll> p,int f,ll mod=MOD){
  int n=a.size();
  m.pb(mod); p.pb(mod);
  vector<ll> d(n+1,1),sum(n+1);
  rep(i,n){
    //    sum[i]+x*d[i]==a[i] mod m[i];
    ll x=(a[i]-sum[i])%m[i]*modpow(d[i],m[i]/p[i]*(p[i]-1)-1,m[i])%m[i];
    //cout<<a[i]<<"-"<<sum[i]<<","<<d[i]<<":";//d[i]おかしい
    if(x<0) x+=m[i];
    //cout<<x<<",";cout<<"["<<d[i]<<"*"<<modpow(d[i],m[i]/p[i]*(p[i]-1)-1,m[i])<<"="<<d[i]*modpow(d[i],m[i]/p[i]*(p[i]-1)-1,m[i])%m[i]<<endl;
    if(f && x==0 && i==0)x=m[i];
    for(int j=i+1;j<=n;++j){
      (sum[j]+=x%m[j]*d[j]%m[j])%=m[j];
      (d[j]*=m[i])%=m[j];
    }
    //cout<<sum<<d;
    //cout<<sum.back()<<endl;
    //rep(j,n)cout<<sum.back()%m[j]<<",";cout<<endl;
  }
  return (sum.back()%MOD+MOD)%MOD;
}

//中国剰余定理
ll china2(const vector<ll> &a,const vector<ll> &m){
  ll p=1,re=0,pp,x,y;
  rep(i,m.size())
    p*=m[i];
  //cout<<p<<"!!!!!!!"<<endl;
  rep(i,m.size()){
    pp=p/m[i];
    extgcd(m[i],pp,x,y);
    (re+=pp*y%p*a[i]%p)%=p;
  }
  return (re%p+p)%p;
}
int updChina(map<ll,pll> &mp,ll a,ll m,ll p){
  //cout<<a<<","<<m<<","<<p<<endl;
  if(mp.count(p)){
    pll tmp=mp[p];
    if((tmp.X-a)%min(tmp.Y,m))
      return 1;
    if(tmp.Y<m)
      mp[p]=pll(a,m);
  }else{
    mp[p]=pll(a,m);
  }
  return 0;
}
//互いに素じゃなくてもよい。解なしは-1
ll china(const vector<ll> &a,const vector<ll> &m,int f=0){
  map<ll,pll> mp;  //PRIME -> REM * MOD
  pll tmp;
  ll num,p=1;
  rep(i,a.size()){
    num=m[i];
    rep(j,primes.size())if(m[i]%primes[j]==0){
      p=1;
      while(num%primes[j]==0){
	p*=primes[j];
	num/=primes[j];
      }
      if(updChina(mp,a[i],p,primes[j]))
	return -1;
    }
    if(num>1)
      if(updChina(mp,a[i],num,num))
	return -1;
  }
  //for(auto t:mp)cout<<t<<",";cout<<endl;
  vector<ll> aa,mm,pp;
  for(auto temp:mp){
    num=temp.Y.X; p=temp.Y.Y;
    aa.pb((num%p+p)%p);
    mm.pb(p);
    pp.pb(temp.X);
  }
  //cout<<aa<<mm;
  return garner(aa,mm,pp,f);
}

int main(){
  ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(0);
  int i,j,k;
  findPrime();
  int n;
  cin>>n;
  vector<ll> a(n),m(n);
  long long te,mp;
  rep(i,n){
    cin>>te>>mp;
    a[i]=te; m[i]=mp;
  }
  ll re=china(a,m),lcm=1;
  //cout<<re<<endl;
  rep(i,n)
    lcm*=m[i]/__gcd(lcm,m[i]);
  //  (re+=lcm)%=lcm;
  if(!re)re=china(a,m,1);
  ll d=1e18;
  long long res=re/d,ult=re%d;
  if(res)
    cout<<res<<ult<<endl;
  else
    cout<<ult<<endl;
  return 0;
}