#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#include <tuple>
#define mkp make_pair
#define mkt make_tuple
#define rep(i,n) for(int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;
const ll MOD=1e9+7;
template<class T> void chmin(T &a,const T &b){if(a>b) a=b;}
template<class T> void chmax(T &a,const T &b){if(a<b) a=b;}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  vector<int> A(4);
  rep(i,4) cin>>A[i];

  sort(A.begin(),A.end());
  for(int i=1;i<4;i++){
    if(A[0]+i!=A[i]){
      cout<<"No"<<endl;
      return 0;
    }
  }
  cout<<"Yes"<<endl;

  return 0;
}