#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]);}
constexpr auto abs(auto x){return x<0?-x:x;}
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>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();}
};
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{
struct dsu_plain{
  ll n_;
  vec<int>par_or_size_;
  dsu_plain(ll n):n_(n),par_or_size_(n,-1){}
  auto merge(ll a,ll b){
    ll x=leader(a),y=leader(b);
    if(x==y)return x;
    if(-par_or_size_[x]<-par_or_size_[y])swap(x,y),swap(a,b);

    par_or_size_[x]+=par_or_size_[y];
    par_or_size_[y]=x;
    return x;
  }
  ll leader(ll a){
    if(par_or_size_[a]<0)return a;
    return par_or_size_[a]=leader(par_or_size_[a]);
  }
  auto groups(){
    vec<int>leader_buf(n_),group_size(n_);
    fo(u,n_){
      leader_buf[u]=leader(u);
      group_size[leader_buf[u]]++;
    }
    vec<vec<int>>res(n_);
    fo(u,n_)res[u].reserve(group_size[u]);
    fo(u,n_)res[leader_buf[u]].eb(u);

    res.erase(remove_if(res.begin(),res.end(),[&](const vec<int>& v){return v.empty();}),res.end());
    return res;
  }
};
}
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){}
  decltype(auto)operator[](ll i)const{return edges_[i];}
  ll size()const{return edges_.size();}
  auto components()const{
    dsu_plain uf(edges_.size());
    fo(u,edges_.size())fe(edges_[u],e)uf.merge(u,e.to_);
    return uf.groups();
  }
  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;}
};
}
namespace my{
template<class WT>bool is_semi_eulerian_directed(const Graph<WT>&g){
  vec<ll>deg(g.size());

  bool has_edge_component=0;
  fe(g.components(),v){
    ll edge_count=0;
    fe(v,u)fe(g[u],e){
      deg[u]--;
      deg[e.to_]++;
      edge_count++;
    }
    if(edge_count==0)continue;
    if(has_edge_component)return 0;
    has_edge_component=1;

    ll deg_m1=0,deg_p1=0;
    fe(v,u){
      if(abs(deg[u])>=2)return 0;
      if(deg[u]==-1)deg_m1++;
      if(deg[u]==+1)deg_p1++;
    }
    if(deg_m1!=1||deg_p1!=1)return 0;
  }
  return 1;
}
template<class WT>bool is_eulerian_directed(const Graph<WT>&g){
  vec<ll>deg(g.size());

  bool has_edge_component=0;
  fe(g.components(),v){
    ll edge_count=0;
    fe(v,u)fe(g[u],e){
      deg[u]--;
      deg[e.to_]++;
      edge_count++;
    }
    if(edge_count==0)continue;
    if(has_edge_component)return 0;
    has_edge_component=1;

    fe(v,u)if(deg[u]!=0)return 0;
  }
  return 1;
}
}
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);

  if(is_eulerian_directed(g))pp(M);
  else if(is_semi_eulerian_directed(g))pp(1);
  else pp(0);
}}