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

const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) for(int i=0;i<(n);++i)
#define REPR(i,n) for(int i=n;i>=0;i--)
#define ALL(v) (v.begin(),v.end())
#define COUT(x) cout<<(x)<<"\n"


int main(){
    int a[4];
    REP(i,4){
        cin >> a[i];
    }
    sort(a,a+4);
    if(a[3]-a[2]==1&&a[2]-a[1]==1&&a[1]-a[0]==1)COUT("Yes");
    else COUT("No");
    return 0;
}