#include<bits/stdc++.h>
#if __has_include(<atcoder/all>)
#endif
using namespace std;
#define eb emplace_back
#define LL(...) ll __VA_ARGS__;lin(__VA_ARGS__)
#define RDVV(T,n,...) vec<T>__VA_ARGS__;fe(refs(__VA_ARGS__),e)e.get().resizes(n);vin(__VA_ARGS__)
#define VV(n,...) RDVV(ll,n,__VA_ARGS__)
#define fo(i,...) for(auto[i,i##stop,i##step]=for_range<ll>(0,__VA_ARGS__);i<i##stop;i+=i##step)
#define fe(a,e,...) for(auto&&__VA_OPT__([)e __VA_OPT__(,__VA_ARGS__]):a)
#define binary_operator(op,type) auto operator op(const type&rhs)const{auto copy=*this;return copy op##=rhs;}
#define defpp template<ostream&o=cout>void pp(const auto&...a){[[maybe_unused]]const char*c="";((o<<c<<a,c=" "),...);o<<'\n';}void epp(const auto&...a){pp<cerr>(a...);}
#define entry defpp void main();void main2();}int main(){my::io();my::main();}namespace my{
namespace my{
void io(){cin.tie(nullptr)->sync_with_stdio(0);cout<<fixed<<setprecision(15);}
using ll=long long;
constexpr auto refs(auto&...a){return array{ref(a)...};}
template<class T>constexpr auto for_range(T s,T b){T a=0;if(s)swap(a,b);return array{a-s,b,1-s*2};}
void lin(auto&...a){(cin>>...>>a);}
void vin(auto&...a){fo(i,(a.size()&...))(cin>>...>>a[i]);}
template<class A,class B=A>struct pair{
  A a;B b;
  pair()=default;
  pair(A a,B b):a(a),b(b){}
  auto operator<=>(const pair&)const=default;
};
template<class F=less<>>auto&sort(auto&a,F f={}){ranges::sort(a,f);return a;}
auto&unique(auto&a){sort(a).erase(ranges::unique(a).begin(),a.end());return a;}
template<class...A>using pack_back_t=tuple_element_t<sizeof...(A)-1,tuple<A...>>;
}
namespace my{
template<class V>concept vectorial=is_base_of_v<vector<typename remove_cvref_t<V>::value_type>,remove_cvref_t<V>>;
template<class V>constexpr int depth=0;
template<class T>struct core_t_helper{using type=T;};
template<class T>using core_t=core_t_helper<T>::type;
template<class V>struct vec;
template<int D,class T>struct hvec_helper{using type=vec<typename hvec_helper<D-1,T>::type>;};
template<class T>struct hvec_helper<0,T>{using type=T;};
template<int D,class T>using hvec=hvec_helper<D,T>::type;
template<class V>struct vec:vector<V>{
  static constexpr int D=depth<V>+1;
  using C=core_t<V>;
  using vector<V>::vector;
  void resizes(const auto&...a){if constexpr(sizeof...(a)==D)*this=make(a...,C{});else{ }}
  static auto make(ll n,const auto&...a){
    if constexpr(sizeof...(a)==1)return vec<C>(n,array{a...}[0]);
    else { }
  }
  auto&operator^=(const vec&u){this->insert(this->end(),u.begin(),u.end());return*this;}
  binary_operator(^,vec)
  ll size()const{return vector<V>::size();}
  auto&emplace_back(auto&&...a){vector<V>::emplace_back(std::forward<decltype(a)>(a)...);return*this;}
  auto lower_bound(const V&x)const{return std::lower_bound(this->begin(),this->end(),x);}
  ll arg_lower_bound(const V&x)const{return lower_bound(x)-this->begin();}
  auto fold(const auto&f)const{
    pair<C,bool>r{};
    fe(*this,e){
      if constexpr(!vectorial<V>){
        if(r.b)f(r.a,e);
        else r={e,1};
      }else { }

    }
    return r;
  }
  auto sum()const{return fold([](auto&a,const auto&b){a+=b;}).a;}
  auto count(C x)const{return is_equal_transform(x).sum();}
  auto transform(const auto&f)const{
    hvec<D,decltype(f(C()))>res(size());
    if constexpr(vectorial<V>){ }
    else std::transform(this->begin(),this->end(),res.begin(),f);
    return res;
  }
  vec is_equal_transform(C x)const{return transform([&](const auto e)->C{return e==x;});}
};
template<class...A>requires(sizeof...(A)>=2)vec(const A&...a)->vec<hvec<sizeof...(A)-2,pack_back_t<A...>>>;
auto zip(auto&...a){auto v=(a^...);unique(v);([&](auto&u){fe(u,e)e=v.arg_lower_bound(e);}(a),...);return v;}
}
namespace my{
template<class WT>struct Edge{
  int from_,to_;
  WT wt_;
  int id_;
  Edge()=default;
  Edge(int from,int to,WT wt=1,int id=-1):from_(from),to_(to),wt_(wt),id_(id){}
};
template<class WT>class Graph{
public:
  vec<vec<Edge<WT>>>edges_;
  Graph()=default;
  Graph(ll n):edges_(n){}
  ll size()const{return edges_.size();}
  auto&add_edges(const vec<ll>&a,const vec<ll>&b){fo(i,a.size())edges_[a[i]].eb(a[i],b[i],1,i);return*this;}
  auto in_deg_enumerate()const{
    vec<ll>res(size());
    fo(u,size())fe(edges_[u],e)++res[e.to_];
    return res;
  }
};
}
namespace my{entry
void main(){
  LL(N);
  VV(N,a,b);
  ll M=zip(a,b).size();

  Graph<ll>g(M);
  g.add_edges(a,b);

  auto deg=g.in_deg_enumerate();
  ll cnt0=deg.count(0);
  if(cnt0==0){
    pp(N);
  }else if(cnt0==1){
    pp(1);
  }else{
    pp(0);
  }
}}