#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define sar(a,n) {cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl;}

using namespace std;

template<typename S,typename T>auto&operator<<(ostream&o,pair<S,T>p){return o<<"{"<<p.fi<<","<<p.se<<"}";}
template<typename T>auto&operator<<(ostream&o,set<T>s){for(auto&e:s)o<<e<<" ";return o;}
template<typename S,typename T,typename U>
auto&operator<<(ostream&o,priority_queue<S,T,U>q){while(!q.empty())o<<q.top()<<" ",q.pop();return o;}
template<typename K,typename T>auto&operator<<(ostream&o,map<K,T>&m){for(auto&e:m)o<<e<<" ";return o;}
template<typename T>auto&operator<<(ostream&o,vector<T>v){for(auto&e:v)o<<e<<" ";return o;}
void ashow(){cout<<endl;}template<typename T,typename...A>void ashow(T t,A...a){cout<<t<<" ";ashow(a...);}
template<typename S,typename T,typename U>
struct TRI{S fi;T se;U th;TRI(){}TRI(S f,T s,U t):fi(f),se(s),th(t){}
bool operator<(const TRI&_)const{return(fi==_.fi)?((se==_.se)?(th<_.th):(se<_.se)):(fi<_.fi);}};
template<typename S,typename T,typename U>
auto&operator<<(ostream&o,TRI<S,T,U>&t){return o<<"{"<<t.fi<<","<<t.se<<","<<t.th<<"}";}

typedef pair<int, int> P;
typedef pair<ll, ll> pll;
typedef TRI<int, int, int> tri;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<P> vp;
typedef vector<double> vd;
typedef vector<string> vs;

const int MAX_N = 32005;

template<class _Key, class _Tp, class _Hash, bool DOWNSIZE> class UnorderedMapIterator;

template<class _Key, class _Tp, class _Hash = hash<_Key>, bool DOWNSIZE = false>
class UnorderedMap
{
private:
    using iterator = UnorderedMapIterator<_Key, _Tp, _Hash, DOWNSIZE>;
    using value_type = _Tp;
    using data_type = pair<_Key, _Tp>;
    using aligned_pointer = typename aligned_storage<sizeof(value_type), alignof(value_type)>::type;
    friend UnorderedMapIterator<_Key, _Tp, _Hash, DOWNSIZE>;
    struct bucket {
        _Key _key;
        short int _dist;
        bool _last, _end;
        aligned_pointer _value_ptr;
        bucket() noexcept : _dist(-1), _last(false), _end(false){}
        bucket& operator=(const bucket& another) noexcept {
            _key = another._key, _dist = another._dist, _last = another._last, _end = another._end;
            if(!another.empty()){
                new(&_value_ptr) value_type(*reinterpret_cast<const value_type*>(&another._value_ptr));
            }
            return *this;
        }
        ~bucket(){ if(!empty()) _delete(); }
        inline void clear() noexcept { _dist = -1; }
        inline void _delete(){ _dist = -1, value_ptr()->~value_type(); }
        inline bool empty() const noexcept { return (_dist == -1); }
        inline value_type& value() noexcept {
            return *reinterpret_cast<value_type*>(&_value_ptr);
        }
        inline value_type* value_ptr() noexcept {
            return reinterpret_cast<value_type*>(&_value_ptr);
        }
        inline void new_value(value_type&& value){
            new(&_value_ptr) value_type(move(value));
        }
    };
    inline static unsigned int ceilpow2(unsigned int u) noexcept {
        --u, u |= u >> 1, u |= u >> 2, u |= u >> 4, u |= u >> 8;
        return (u | (u >> 16)) + 1;
    }
    inline static bucket *increment(bucket *cur) noexcept {
        for(++cur; !cur->_end; ++cur){
            if(!cur->empty()) break;
        }
        return cur;
    }
    inline bucket *next_bucket(bucket *cur) const noexcept {
        return cur->_last ? _buckets : cur + 1;
    }
    inline unsigned int make_hash(const _Key& key) const noexcept {
        return _Hash()(key);
    }
    inline float load_rate() const noexcept {
        return (float)_data_count / _bucket_count;
    }
    bucket *insert(bucket *cur, _Key&& key, short int dist, value_type&& value){
        bucket *ret = cur;
        bool flag = false;
        while(true){
            if(cur->empty()){
                cur->_key = move(key), cur->_dist = dist, cur->new_value(move(value));
                if(!flag) ret = cur, flag = true;
                break;
            }else if(dist > cur->_dist){
                swap(key, cur->_key), swap(dist, cur->_dist), swap(value, cur->value());
                if(!flag) ret = cur, flag = true;
            }
            ++dist;
            cur = next_bucket(cur);
        }
        return ret;
    }
    template<class Key>
    bucket *_find(Key&& key, bool push = false){
        unsigned int hash = make_hash(key);
        bucket *cur = _buckets + (hash & _mask);
        short int dist = 0;
        while(dist <= cur->_dist){
            if(key == cur->_key) return cur;
            ++dist, cur = next_bucket(cur);
        }
        if(!push) return _buckets + _bucket_count;
        ++_data_count;
        if(rehash_check()){
            cur = _buckets + (hash & _mask), dist = 0;
        }
        value_type new_value = value_type();
        _Key new_key = forward<Key>(key);
        return insert(cur, move(new_key), dist, move(new_value));
    }
    template<class Data>
    bucket *find_insert(Data&& data){
        const _Key& key = data.first;
        unsigned int hash = make_hash(key);
        bucket *cur = _buckets + (hash & _mask);
        short int dist = 0;
        while(dist <= cur->_dist){
            if(key == cur->_key) return cur;
            ++dist, cur = next_bucket(cur);
        }
        ++_data_count;
        if(rehash_check()){
            cur = _buckets + (hash & _mask), dist = 0;
        }
        data_type new_data = forward<Data>(data);
        return insert(cur, move(new_data.first), dist, move(new_data.second));
    }
    template<typename... Args>
    bucket *emplace(Args&&... args){
        return find_insert(data_type(forward<Args>(args)...));
    }
    bucket *backward_shift(bucket *cur, bool next_ret){
        bucket *next = next_bucket(cur), *ret = cur;
        if(next->_dist < 1) return next_ret ? increment(cur) : cur;
        do {
            cur->_key = next->_key, cur->_dist = next->_dist - 1;
            cur->new_value(move(next->value()));
            cur = next, next = next_bucket(cur);
        }while(next->_dist >= 1);
        cur->clear();
        return ret;
    }
    bucket *erase_impl(bucket *cur, bool next_ret){
        assert(static_cast<size_t>(cur - _buckets) != _bucket_count);
        cur->_delete();
        --_data_count;
        return backward_shift(cur, next_ret);
    }
    bucket *erase_itr(bucket *cur, bool next_ret = true){
        const _Key key = cur->_key;
        return erase_impl(rehash_check() ? _find(key) : cur, next_ret);
    }
    bucket *erase_key(const _Key& key, bool next_ret = true){
        rehash_check();
        return erase_impl(_find(key), next_ret);
    }
    bool rehash_check(){
        if(load_rate() >= MAX_LOAD_RATE){
            rehash(_bucket_count * 2u);
            return true;
        }else if(DOWNSIZE){
            if(load_rate() <= MIN_LOAD_RATE && _bucket_count >= DOWNSIZE_THRESHOLD){
                rehash(_bucket_count / 2u);
                return true;
            }
        }
        return false;
    }
    void move_data(bucket *cur){
        insert(_buckets + (make_hash(cur->_key) & _mask), move(cur->_key), 0, move(cur->value()));
    }
    void rehash(unsigned int new_bucket_count){
        UnorderedMap new_unordered_map(new_bucket_count);
        new_unordered_map._data_count = _data_count;
        for(bucket *cur = _buckets; !cur->_end; ++cur){
            if(!cur->empty()){
                new_unordered_map.move_data(cur);
            }
        }
        swap(*this, new_unordered_map);
    }
    friend void swap(UnorderedMap& ump1, UnorderedMap& ump2){
        swap(ump1._bucket_count, ump2._bucket_count);
        swap(ump1._mask, ump2._mask);
        swap(ump1._data_count, ump2._data_count);
        swap(ump1._buckets, ump2._buckets);
    }

private:
    unsigned int _bucket_count, _mask, _data_count;
    bucket *_buckets;
public:
    const float MAX_LOAD_RATE = 0.5f;
    const float MIN_LOAD_RATE = 0.1f;
    const unsigned int DOWNSIZE_THRESHOLD = 16u;
    UnorderedMap(unsigned int bucket_size = 1u)
     : _bucket_count(ceilpow2(max(bucket_size, 1u))), _mask(_bucket_count - 1),
        _data_count(0u), _buckets(new bucket[_bucket_count + 1]){
        _buckets[_bucket_count - 1]._last = true, _buckets[_bucket_count]._end = true;
    }
    UnorderedMap(const UnorderedMap& another)
        : _bucket_count(another._bucket_count), _mask(another._mask), _data_count(another._data_count){
        _buckets = new bucket[_bucket_count + 1u];
        for(unsigned int i = 0u; i <= _bucket_count; ++i){
            _buckets[i] = another._buckets[i];
        }
    }
    UnorderedMap(UnorderedMap&& another)
        : _bucket_count(move(another._bucket_count)), _mask(move(another._mask)),
            _data_count(move(another._data_count)), _buckets(another._buckets){
        another._buckets = nullptr;
    }
    UnorderedMap& operator=(const UnorderedMap& another){
        delete[] _buckets;
        _bucket_count = another._bucket_count;
        _mask = another._mask;
        _data_count = another._data_count;
        _buckets = new bucket[_bucket_count + 1u];
        for(unsigned int i = 0u; i <= _bucket_count; ++i){
            _buckets[i] = another._buckets[i];
        }
        return *this;
    }
    UnorderedMap& operator=(UnorderedMap&& another){
        delete[] _buckets;
        _bucket_count = move(another._bucket_count);
        _mask = move(another._mask);
        _data_count = move(another._data_count);
        _buckets = another._buckets;
        another._buckets = nullptr;
        return *this;
    }
    ~UnorderedMap(){ delete[] _buckets; }
    friend ostream& operator<< (ostream& os, UnorderedMap& ump) noexcept {
        for(auto val : ump) os << '{' << val.first << ',' << val.second << "} ";
        return os;
    }
    _Tp& operator[](const _Key& key){ return _find(key, true)->value(); }
    _Tp& operator[](_Key&& key){ return _find(move(key), true)->value(); }
    const _Tp& at(const _Key& key){
        bucket *res = _find(key);
        if(res == _buckets + _bucket_count) __throw_out_of_range(__N("Unordered_Map::at"));
        return res->value();
    }
    void clear(){
        UnorderedMap new_unordered_map(1u);
        swap(*this, new_unordered_map);
    }
    size_t size() const noexcept { return _data_count; }
    size_t bucket_count() const noexcept { return _bucket_count; }
    bool empty() const noexcept { return (_data_count == 0); }
    iterator begin() noexcept { return _buckets->empty() ? iterator(increment(_buckets)) : iterator(_buckets); }
    iterator end() noexcept { return iterator(_buckets + _bucket_count); }
    iterator find(const _Key& key){ return iterator(_find(key)); }
    iterator insert(const data_type& data){ return iterator(find_insert(data)); }
    iterator insert(data_type&& data){ return iterator(find_insert(move(data))); }
    template<typename... Args>
    iterator emplace(Args&&... args){ return iterator(_emplace(forward<Args>(args)...)); }
    iterator erase(const _Key& key){ return iterator(erase_key(key)); }
    iterator erase(const iterator& itr){ return iterator(erase_itr(itr.bucket_ptr)); }
    void simple_erase(const _Key& key){ erase_key(key, false); }
    void simple_erase(const iterator& itr){ erase_itr(itr.bucket_ptr, false); }

    // DEBUG 用
    short int maximum_distance() const noexcept {
        short int ret = -1;
        for(bucket *cur = _buckets; !cur->_end; ++cur){
            ret = max(ret, cur->_dist);
        }
        return ret;
    }
};

template<class _Key, class _Tp, class _Hash, bool DOWNSIZE>
class UnorderedMapIterator {
private:
    friend UnorderedMap<_Key, _Tp, _Hash, DOWNSIZE>;
    typename UnorderedMap<_Key, _Tp, _Hash, DOWNSIZE>::bucket *bucket_ptr;
    using iterator_category = forward_iterator_tag;
    using value_type = pair<const _Key, _Tp>;
    using difference_type = ptrdiff_t;
    using reference = pair<const _Key&, _Tp&>;

private:
    UnorderedMapIterator(typename UnorderedMap<_Key, _Tp, _Hash, DOWNSIZE>::bucket *_bucket_ptr)
        noexcept : bucket_ptr(_bucket_ptr){}
public:
    UnorderedMapIterator() noexcept : bucket_ptr(){}
    UnorderedMapIterator(const UnorderedMapIterator& itr) noexcept : bucket_ptr(itr.bucket_ptr){}
    UnorderedMapIterator& operator=(const UnorderedMapIterator& itr)
        & noexcept { return bucket_ptr = itr.bucket_ptr, *this; }
    UnorderedMapIterator& operator=(const UnorderedMapIterator&& itr)
        & noexcept { return bucket_ptr = itr.bucket_ptr, *this; }
    reference operator*() const noexcept { return {bucket_ptr->_key, bucket_ptr->value()}; }
    UnorderedMapIterator& operator++() noexcept {
        return bucket_ptr = UnorderedMap<_Key, _Tp, _Hash, DOWNSIZE>::increment(bucket_ptr), *this;
    }
    UnorderedMapIterator operator++(int) const noexcept {
        return UnorderedMapIterator(UnorderedMap<_Key, _Tp, _Hash, DOWNSIZE>::increment(this->bucket_ptr));
    }
    bool operator==(const UnorderedMapIterator& itr) const noexcept { return !(*this != itr); };
    bool operator!=(const UnorderedMapIterator& itr) const noexcept { return bucket_ptr != itr.bucket_ptr; }
};

template<typename T>
T mod_add(const T a, const T b, const T mod){
    return (a + b) % mod;
}

template<typename T>
T mod_mul(const T a, const T b, const T mod){
    return a * b % mod;
}

template<typename T>
T mod_pow(T a, T b, const T mod){
    T res = 1;
    while(b){
        if(b & 1){
            res = mod_mul(res, a, mod);
        }
        a = mod_mul(a, a, mod);
        b >>= 1;
    }
    return res;
}

template<typename T>
T mod_inv(T a, T mod){
    T u[] = {a, 1, 0}, v[] = {mod, 0, 1}, t;
    while(*v){
        t = *u / *v;
        swap(u[0] -= t * v[0], v[0]);
        swap(u[1] -= t * v[1], v[1]);
        swap(u[2] -= t * v[2], v[2]);
    }
    u[1] %= mod;
    return (u[1] < 0) ? (u[1] + mod) : u[1];
}

bool flag;

template<typename T>
T garner(const vector<T>& a, vector<T> p, const T mod){
    const unsigned int sz = a.size();
    vector<T> kp(sz + 1, 0), rmult(sz + 1, 1);
    p.push_back(mod);
    for(unsigned int i = 0; i < sz; ++i){
        T x = mod_mul(a[i] - kp[i], mod_inv(rmult[i], p[i]), p[i]);
        x = (x < 0) ? (x + p[i]) : x;
        for(unsigned int j = i + 1; j < sz + 1; ++j){
            kp[j] = mod_add(kp[j], rmult[j] * x, p[j]);
            rmult[j] = mod_mul(rmult[j], p[i], p[j]);
        }
    }
    if(flag) return rmult[sz];
    return kp[sz];
}

vector<int> prime;
bool is_prime[MAX_N];

void sieve(int n){
	for(int i=0;i<=n;i++){
		is_prime[i] = true;
	}
	is_prime[0] = is_prime[1] = false;
	for(int i=2;i<=n;i++){
		if(is_prime[i]){
			prime.push_back(i);
			for(int j=2*i;j<=n;j+=i){
				is_prime[j] = false;
			}
		}
	}
}

signed main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    sieve(32000);
    UnorderedMap<int, vp> mp;
    flag = true;
    rep(i,n){
        int x, y;
        cin >> x >> y;
        if(x) flag = false;
        for(int p : prime){
            if(y % p) continue;
            int mult = 1;
            do{
                y /= p, mult *= p;
            }while(y % p == 0);
            mp[p].emplace_back(x % mult, mult);
        }
        if(y > 1) mp[y].emplace_back(x % y, y);
    }
    vl x, y;
    for(const auto& it : mp){
        int a = 0, b = 0;
        for(const P& p : it.se){
            if(a < p.se) a = p.se, b = p.fi;
        }
        for(const P& p : it.se){
            if(p.fi != b % p.se){
                cout << "-1\n";
                return 0;
            }
        }
        x.pb(b), y.pb(a);
    }
    cout << garner(x, y, (long long)MOD) << "\n";
    return 0;
}