#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvvl vector<vvl>
#define vvl vector<vector<ll>>
#define VV(a, b, c, d) vector<vector<d>>(a, vector<d>(b, c))
#define VVV(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define re(c, b) for(ll c=0;c<b;c++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

int main(int argc, char const *argv[]) {
  vll a(4);re(i, 4) std::cin >> a[i];
  sort(all(a));
  bool f = a[1] == a[0] + 1 && a[2] == a[1] + 1 && a[3] == a[2] + 1;
  std::cout << (f?"Yes":"No") << '\n';

}