#include "bits/stdc++.h"
using namespace std;
typedef long long ll;

int main() {
    vector<int> a(4);
    for (int i = 0; i < 4; i++) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());
    if (a[0] == a[1] - 1 && a[1] == a[2] - 1 && a[2] == a[3] - 1) {
        puts("Yes");
    }
    else {
        puts("No");
    }
    return 0;
}