#include <bits/stdc++.h>
#ifdef _DEBUG
#include "debug.hpp"
#else
#define debug(...)
#endif
#define fastIO (cin.tie(0), cout.tie(0), ios::sync_with_stdio(false))
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define precise(i) fixed << setprecision(i)
using ill = int64_t;
using ull = uint64_t;
using namespace std;
using std::cout;

void solve() {
  vector<ull> A(4);
  for (auto &a : A) cin >> a;
  sort(A.begin(), A.end());
  if (A.at(0) + 1 == A.at(1) && A.at(1) + 1 == A.at(2) &&
      A.at(2) + 1 == A.at(3)) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
}

void wrapper() {
  rep(i, 2) {
    cout << "[TEST " << (i + 1) << "]\n";
    solve();
    cout << "\n";
  }
}

int main() {
  fastIO;
#ifdef _DEBUG
  wrapper();
#else
  solve();
#endif
}