#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main(){
  vector<int> A(4);
  for(int i = 0; i < 4; ++i) cin >> A[i];
  sort(A.begin(), A.end());
  for(int i = 1; i < 4; ++i){
    if(A[i]-1 != A[i-1]){
      puts("No");
      return 0;
    }
  }
  puts("Yes");
}