#include<bits/stdc++.h> using namespace std; #define rep(i,n) for(ll i=0;i<(n);++i) using ll = int_fast64_t; using pll = pair<ll,ll>; constexpr ll INF = 1LL<<60; constexpr ll MOD = 1e9+7; template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;} template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}return 0;} #if loc||local void dump(){cerr<<endl;} template<class T,class... Ts> void dump(T&& h, Ts&&... t){cerr<<h<<", ";dump(forward<Ts>(t)...);} #else void dump(){} template<class T,class... Ts> void dump(T&& h, Ts&&... t){} #endif template<class T> istream &operator>>(istream&is,vector<T>&v){for(auto &elemnt:v)is>>elemnt;return is;} template<class T,class U> istream &operator>>(istream&is,pair<T,U>&p){is>>p.first>>p.second;return is;} template<class T> ostream &operator<<(ostream& os,vector<T>const& v){for(auto const& vi:v)os<<vi<<" ";return os;} template<class T,class U> ostream &operator<<(ostream& os,pair<T,U>const& p){os<<p.first<<","<<p.second;return os;} template<class T>vector<T> vec(size_t a){return vector<T>(a);} template<class T, class... Ts>auto vec(size_t a, Ts... ts){return vector<decltype(vec<T>(ts...))>(a, vec<T>(ts...));} signed main(){ int n = 4; vector<int> a(n); cin>>a; sort(begin(a),end(a)); vector<int> b(n); iota(b.begin(),b.end(),a[0]); cout<<(a==b?"Yes":"No")<<endl; }