#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <cmath>
#include <climits>
#include <iomanip>
#include <set>
#include <map>
using namespace std;
typedef long long ll;
int main(){
    vector<ll> a(4);
    cin >> a[0] >> a[1] >> a[2] >> a[3];
    sort(a.begin(),a.end());
    if(a[3] - a[2] == 1 && a[2] - a[1] == 1 && a[1] - a[0] == 1)cout << "Yes" << endl;
    else cout << "No" << endl;
}