#include<bits/stdc++.h>
using namespace std;
#define endl "\n"
typedef long long int ll;

const int MAX = 1e5+7, MOD = 1e9+7;
void solve() {
	int x;cin>>x;
	if(x<=50){
		cout<<"YES\n";
	} else {
		cout<<"NO\n";
	}
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
 
  int t = 1;
  // cin >> t;
  for (int tc = 1; tc <= t; tc++) {
    //cout<<"case "<<tc<<": ";
    solve();
  }
  return 0;
}