#include <bits/stdc++.h>
using namespace std;
// #define LOCAL // 提出時はコメントアウト
#define DEBUG_

typedef long long ll;
const double EPS = 1e-9;
const ll INF = ((1LL<<62)-(1LL<<31));
typedef vector<ll> vecl;
typedef pair<ll, ll> pairl;
template<typename T, typename U> using mapv = map<T,vector<U>>;

#define ALL(v) v.begin(), v.end()
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define contains(S,x) find(ALL(S),x) != S.end()
ll llceil(ll a,ll b) { return (a+b-1)/b; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> vector<vector<T>> genarr(ll n, ll m, T init) { return vector<vector<T>>(n,vector<T>(m,init)); }

///// DEBUG
#define DUMPOUT cerr
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
template<typename T>istream&operator>>(istream&is,vector<T>&vec){for(T&x:vec)is>>x;return is;}
template<typename T,typename U>ostream&operator<<(ostream&os,pair<T,U>&pair_var){os<<"("<<pair_var.first<<", "<<pair_var.second<<")";return os;}
template<typename T>ostream&operator<<(ostream&os,const vector<T>&vec){os<<"{";for(int i=0;i<vec.size();i++){os<<vec[i]<<(i+1==vec.size()?"":", ");}
os<<"}";return os;}
template<typename T,typename U>ostream&operator<<(ostream&os,map<T,U>&map_var){os<<"{";repi(itr,map_var){os<<*itr;itr++;if(itr!=map_var.end())os<<", ";itr--;}
os<<"}";return os;}
template<typename T>ostream&operator<<(ostream&os,set<T>&set_var){os<<"{";repi(itr,set_var){os<<*itr;itr++;if(itr!=set_var.end())os<<", ";itr--;}
os<<"}";return os;}
void dump_func(){DUMPOUT<<endl;}
template<class Head,class...Tail>void dump_func(Head&&head,Tail&&...tail){DUMPOUT<<head;if(sizeof...(Tail)>0){DUMPOUT<<", ";}
dump_func(std::move(tail)...);}
#ifndef LOCAL
#undef DEBUG_
#endif
#ifdef DEBUG_
#define DEB
#define dump(...)                                                          \
DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
        << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
        << endl                                                            \
        << "    ",                                                         \
    dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

//////////



/// ACL Math: https://atcoder.github.io/ac-library/production/document_ja/math.html

// @param m `1 <= m`
// @return x mod m
constexpr long long safe_mod(long long x, long long m) {
    x %= m;
    if (x < 0) x += m;
    return x;
}


// @param b `1 <= b`
// @return pair(g, x) s.t. g = gcd(a, b), xa = g (mod b), 0 <= x < b/g
constexpr std::pair<long long, long long> inv_gcd(long long a, long long b) {
    a = safe_mod(a, b);
    if (a == 0) return {b, 0};

    // Contracts:
    // [1] s - m0 * a = 0 (mod b)
    // [2] t - m1 * a = 0 (mod b)
    // [3] s * |m1| + t * |m0| <= b
    long long s = b, t = a;
    long long m0 = 0, m1 = 1;

    while (t) {
        long long u = s / t;
        s -= t * u;
        m0 -= m1 * u;  // |m1 * u| <= |m1| * s <= b

        // [3]:
        // (s - t * u) * |m1| + t * |m0 - m1 * u|
        // <= s * |m1| - t * u * |m1| + t * (|m0| + |m1| * u)
        // = s * |m1| + t * |m0| <= b

        auto tmp = s;
        s = t;
        t = tmp;
        tmp = m0;
        m0 = m1;
        m1 = tmp;
    }
    // by [3]: |m0| <= b/g
    // by g != b: |m0| < b/g
    if (m0 < 0) m0 += b / s;
    return {s, m0};
}

// 中国剰余: x ≡ y (mod z)の時、{y,z}を返す
// 解が存在しない場合はy=0を返す
std::pair<long long, long long> crt(const std::vector<long long>& r,
                                    const std::vector<long long>& m) {
    assert(r.size() == m.size());
    int n = int(r.size());
    // Contracts: 0 <= r0 < m0
    long long r0 = 0, m0 = 1;
    for (int i = 0; i < n; i++) {
        assert(1 <= m[i]);
        long long r1 = safe_mod(r[i], m[i]), m1 = m[i];
        if (m0 < m1) {
            std::swap(r0, r1);
            std::swap(m0, m1);
        }
        if (m0 % m1 == 0) {
            if (r0 % m1 != r1) return {0, 0};
            continue;
        }
        // assume: m0 > m1, lcm(m0, m1) >= 2 * max(m0, m1)

        // (r0, m0), (r1, m1) -> (r2, m2 = lcm(m0, m1));
        // r2 % m0 = r0
        // r2 % m1 = r1
        // -> (r0 + x*m0) % m1 = r1
        // -> x*u0*g % (u1*g) = (r1 - r0) (u0*g = m0, u1*g = m1)
        // -> x = (r1 - r0) / g * inv(u0) (mod u1)

        // im = inv(u0) (mod u1) (0 <= im < u1)
        long long g, im;
        std::tie(g, im) = inv_gcd(m0, m1);

        long long u1 = (m1 / g);
        // |r1 - r0| < (m0 + m1) <= lcm(m0, m1)
        if ((r1 - r0) % g) return {0, 0};

        // u1 * u1 <= m1 * m1 / g / g <= m0 * m1 / g = lcm(m0, m1)
        long long x = (r1 - r0) / g % u1 * im % u1;

        // |r0| + |m0 * x|
        // < m0 + m0 * (u1 - 1)
        // = m0 + m0 * m1 / g - m0
        // = lcm(m0, m1)
        r0 += x * m0;
        m0 *= u1;  // -> lcm(m0, m1)
        if (r0 < 0) r0 += m0;
    }
    return {r0, m0};
}

long long floor_sum(long long n, long long m, long long a, long long b) {
    long long ans = 0;
    if (a >= m) {
        ans += (n - 1) * n * (a / m) / 2;
        a %= m;
    }
    if (b >= m) {
        ans += n * (b / m);
        b %= m;
    }

    long long y_max = (a * n + b) / m, x_max = (y_max * m - b);
    if (y_max == 0) return ans;
    ans += (n - (x_max + a - 1) / a) * y_max;
    ans += floor_sum(y_max, a, m, (a - x_max % a) % a);
    return ans;

}

const ll MOD = 1e9+7;

int main() {


    ll N;
    cin>>N;

    vecl X(N),Y(N);
    rep(i,N) {
        cin>>X[i]>>Y[i];
    }

    auto [ans,_] = crt(X,Y);
    if (ans == 0) {
        ll zeros = 0;
        rep(i,N) {
            zeros += X[i] == 0;
        }

        if (zeros != X.size()) {
            cout << -1 << endl;
            exit(0);
        }
    }

    cout << ans % MOD << endl;
    
    
    return 0;
}