#include <bits/stdc++.h> using namespace std; typedef long long ll; #define pb push_back #define fi first #define se second typedef pair<ll,ll> P; using VP = vector<P>; using VVP = vector<VP>; using VI = vector<ll>; using VVI = vector<VI>; using VVVI = vector<VVI>; const int inf=1e9+7; const ll INF=1LL<<61; const ll mod=1e9+7; 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; } int main(){ int i,j; int v[4]; for(i=0;i<4;i++) cin>>v[i]; sort(v,v+4); if(v[1]==v[0]+1&&v[2]==v[0]+2&&v[3]==v[0]+3) cout<<"Yes"<<endl; else cout<<"No"<<endl; }