#include <bits/stdc++.h>
using ll = long long int;
using namespace std;
ll mod=1e9+7;
       

int main(){
  int a[4];
  bool ans=0;
  for(int i=0;i<4;i++){
     cin >> a[i];
  }
  do{
    for(int i=0;i<4;i++){
      if(a[0]==a[1]-1 && a[1] == a[2]-1 && a[2]==a[3]-1){ans=1;}
      if(a[0]-1==a[1] && a[1]-1 == a[2] && a[2]-1==a[3]){ans=1;}
    }
  }while(next_permutation(a,a+4));
  if(ans==1){cout << "Yes" << endl;}else{cout << "No" << endl;}
}