#include <bits/stdc++.h>
#include <iostream>
#include <string>
#include <stdio.h>
#include <math.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using ll = long long;
typedef long double ld;
using namespace std;
ll gcd(ll P, ll Q){
    return Q ? gcd(Q,P % Q):P;
}
ll lcm(ll P, ll Q){
     return P / gcd(P,Q) * Q;
}
int main() {
  int P[4];
  cin >> P[0] >> P[1] >> P[2] >> P[3];
  for(int i = 0; i < 4; i++) {
    for(int j = 3; j > i; j--) {
      if(P[j] < P[j - 1]) {
         swap(P[i],P[j]);
      }
    }
  }
    if(P[3] - P[2] == 1 && P[2] - P[1] == 1 && P[1] - P[0] == 1){
      cout << "Yes" << endl;
    }
    else{
      cout << "No" << endl;
    }
  return 0;
}