#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
/*
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
*/
using namespace std;
//--------------------------------------------------------------------
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define overload4(_1,_2,_3,_4,name,...) name
#define rep1(n) for(ll _=0;_<(ll)n;++_)
#define rep2(i,n) for(ll i=0;i<(ll)n;++i)
#define rep3(i,a,b) for(ll i=(ll)a;i<(ll)b;++i)
#define rep4(i,a,b,c) for(ll i=(ll)a;i<(ll)b;i+=(ll)c)
#define rep(...) overload4(__VA_ARGS__,rep4,rep3,rep2,rep1)(__VA_ARGS__)
#ifdef _DEBUG
#define pass(...) __VA_ARGS__ ;

#define debug1(a) cerr<<#a<<": "<<a<<"\n"
#define debug2(a,b) cerr<<#a<<": "<<a<<", "<<#b<<": "<<b<<"\n"
#define debug3(a,b,c) cerr<<#a<<": "<<a<<", "<<#b<<": "<<b<<", "<<#c<<": "<<c<<"\n"
#define debug4(a,b,c,d) cerr<<#a<<": "<<a<<", "<<#b<<": "<<b<<", "<<#c<<": "<<c<<", "<<#d<<": "<<d<<"\n"

/*
#define debug1(a) cout<<#a<<": "<<a<<"\n"
#define debug2(a,b) cout<<#a<<": "<<a<<", "<<#b<<": "<<b<<"\n"
#define debug3(a,b,c) cout<<#a<<": "<<a<<", "<<#b<<": "<<b<<", "<<#c<<": "<<c<<"\n"
#define debug4(a,b,c,d) cout<<#a<<": "<<a<<", "<<#b<<": "<<b<<", "<<#c<<": "<<c<<", "<<#d<<": "<<d<<"\n"
*/

#define debug(...) overload4(__VA_ARGS__,debug4,debug3,debug2,debug1)(__VA_ARGS__)
#define koko cerr << "koko\n";
#else
#define debug(...) void(0)
#define pass(...) void(0);
#define koko void(0);
#endif
#define mp make_pair
//#define fi first
//#define se second
void myset(){ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);}
void doset(int n){cout << fixed << setprecision(n);cerr << fixed << setprecision(n);}
using ll = long long;
using ld = long double;
using dou = double;
template<class First,class Second>ostream& operator<<(ostream& os,const pair<First,Second>& pp)
{return os << "{" << pp.first << "," << pp.second << "}";}
template<class T>ostream& operator<<(ostream& os,const vector<T>& VV)
{if(VV.empty())return os<<"[]";os<<"[";rep(i,VV.size())os<<VV[i]<<(i==int(VV.size()-1)?"]":",");return os;}
template<class T>ostream& operator<<(ostream& os,const set<T>& SS)
{if(SS.empty())return os<<"[]";os<<"[";auto ii=SS.begin();for(;ii!=SS.end();ii++)os<<*ii<<(ii==prev(SS.end())?"]":",");return os;}
template<class Key,class Tp>ostream& operator<<(ostream& os,const map<Key,Tp>& MM)
{if(MM.empty())return os<<"[]";os<<"[";auto ii=MM.begin();for(;ii!=MM.end();ii++)os<<"{"<<ii->first<<":"<<ii->second<<"}"<<(ii==prev(MM.end())?"]":",");return os;}
const int inf = 1 << 30;
const ll INF = 1LL << 61;
const ld pi = 3.14159265358;
const ll mod1 = 1000000007LL;
const ll mod2 = 998244353LL;
typedef pair<ll,ll> P;
template<class T, class U> inline bool chmin(T& a, const U& b){ if(a > b){ a = b; return 1; } return 0; }
template<class T, class U> inline bool chmax(T& a, const U& b){ if(a < b){ a = b; return 1; } return 0; }
ll modpow(ll n,ll m,ll MOD){
    if(m == 0)return 1;
    if(m < 0)return 0;
    ll res = 1;
    n %= MOD;
    while(m){
        if(m & 1)res = (res * n) % MOD;
        m >>= 1;
        n *= n;
        n %= MOD;
    }
    return res;
}
ll mypow(ll n,ll m){
    if(m == 0)return 1;
    if(m < 0)return -1;
    ll res = 1;
    while(m){
        if(m & 1)res = (res * n);
        m >>= 1;
        n *= n;
    }
    return res;
}

inline bool isp(ll n){
    bool res = true;
    if(n == 1 || n == 0)return false;
    else{
        for(ll i = 2;i * i <= n;i++){
            if(n % i == 0){
                res = false;
                break;
            }
        }
        return res;
    }
}
inline bool Yes(bool b = 1){cout << (b ? "Yes\n":"No\n");return b;}
inline bool YES(bool b = 1){cout << (b ? "YES\n":"NO\n");return b;}
map<ll,ll> primefactor(ll n){
    map<ll,ll> ma;
    if(n <= 1)return ma;
    ll m = n;
    for(ll i = 2;i * i <= n;i++){
        while(m % i == 0){
            ma[i]++;
            m /= i;
        }
    }
    if(m != 1)ma[m]++;
    return ma;
}
vector<ll> divisor(ll n,bool sorted = true,bool samein = false){
    vector<ll> res;
    for(ll i = 1;i * i <= n;i++){
        if(n % i == 0){
            res.push_back(i);
            if(i * i != n || samein)res.push_back(n / i);
        }
    }
    if(sorted)sort(all(res));
    return res;
}

ll __lcm(ll a,ll b){return a / __gcd(a,b) * b;}

template<class T>T sum(const vector<T> &V){T r=0;for(auto x:V)r+=x;return r;}
template<class T>T sum(const initializer_list<T> &V){T r=0;for(auto x:V)r+=x;return r;}

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


long long extgcd(long long a,long long b,long long &x,long long &y){
    if(b == 0){
        x = 1;
        y = 0;
        return a;
    }
    long long d = extgcd(b,a % b,y,x);
    y -= a / b * x;
    return d;
}
long long modinv(long long a,long long p){
    long long x,y;
    extgcd(a,p,x,y);
    return (x % p + p) % p;
}
long long pregarner(std::vector<long long> &rems,std::vector<long long> &mods,long long MOD){
    for(int i = 0;i < int(rems.size());i++){
        for(int j = 0;j < i;j++){
            long long g = std::gcd(mods[i],mods[j]);
            if((rems[i] - rems[j]) % g != 0)return -1;
            mods[i] /= g;mods[j] /= g;
            long long gi = std::gcd(g,mods[i]),gj = g / gi;
            do{
                g = std::gcd(gi,gj);
                gi *= g;gj /= g;
            }while(g != 1);
            mods[i] *= gi;mods[j] *= gj;
            rems[i] %= mods[i];rems[j] %= mods[j];
        }
    }
    long long res = 1;
    for(long long &a : mods)res = res * a % MOD;
    return res;
}
long long garner(std::vector<long long> rems,std::vector<long long> mods,long long MOD){
    mods.push_back(MOD);
    int sz = mods.size();
    std::vector<long long> cof(sz,1LL),con(sz,0LL);
    for(int i = 0;i < sz - 1;i++){
        long long cur = (rems[i] - con[i]) * modinv(cof[i],mods[i]) % mods[i];
        if(cur < 0)cur += mods[i];
        for(int j = i + 1;j < sz;j++){
            con[j] = (con[j] + cur * cof[j]) % mods[j];
            cof[j] = cof[j] * mods[i] % mods[j];
        }
    }
    return con.back();
}


int main(){
    myset();
    int N;
    cin >> N;
    vector<ll> rems(N),mods(N);
    rep(i,N)cin >> rems[i] >> mods[i];
    bool zero = 1;
    rep(i,N)if(rems[i])zero = 0;
    ll lcm = pregarner(rems,mods,mod1);
    if(zero)cout << lcm << "\n";
    else if(lcm == -1)cout << "-1\n";
    else cout << garner(rems,mods,mod1) << "\n";
}