#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int a[4];
    rep(i,4)cin >> a[i];
    sort(a,a+4);
    int flag = 1;
    rep(i,3)if(a[i] != a[i+1] - 1)flag = 0;
    if(flag)yn;
    return 0;
}