#include "bits/stdc++.h"
using namespace std;
#define Would
#define you
#define all(n)  n.begin(),n.end()
#define rall(n) n.rbegin(),n.rend()
typedef long long ll;
const ll INF = 2147483647;
const ll MOD = 1e9 + 7;
const double EPS = 1e-10;
const double pi = acos(-1);//3.1415...
const ll SIZE = 2000005;
int dx[] = { 1,0,-1,0 }, dy[] = { 0,1,0,-1 }, alp[30];
ll fac[SIZE], finv[SIZE], inv[SIZE];
vector<ll>dij;
struct edge { ll to, cost; };
vector<vector<edge>>G;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

template<typename T>
auto mod_pow(T a, T b) {
	ll res = 1, mul = a;
	for (int i = 0; i < 31; ++i) {
		if (b >> i & 1) {
			res *= mul;
			res %= MOD;
		}
		mul = (mul * mul) % MOD;
	}
	return res;
}

void addedge(int from, int to, int cost) {
	G[from].push_back({ to,cost });
	G[to].push_back({ from,cost });
}

template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }

template<typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
	return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

template<typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type
fill_v(T & t, const V & v) { t = v; }

template<typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type
fill_v(T & t, const V & v) {
	for (auto& e : t) fill_v(e, v);
}

template<typename T>
void outp(vector<T>v) {
	for (int i = 0; i < v.size(); ++i) {
		cout << v[i];
		if (i != v.size() - 1) { cout << " "; }
	}
}

double add(double a, double b) {
	if (abs(a + b) < EPS * (abs(a) + abs(b))) { return 0; }
	return a + b;
}

double len(int a, int b, int c, int d) {
	return (double)sqrt((a - c) * (a - c) + (b - d) * (b - d));
}

int main() {
	int k[5];
	for (int i = 0; i < 4; ++i) { cin >> k[i]; }
	sort(k, k + 4);
	for (int i = 1; i < 4; ++i) { if (k[i] - 1 != k[i - 1]) { cout << "No" << endl; return 0; } }
	cout << "Yes" << endl;
}