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

#define ll long long
#define all(x) (x).begin(), (x).end()
#define f(i, n) for (int i = 0; i < n; i++)
#define trace(x) cerr << #x << ": " << x << '\n'
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    cin >> n;
    n > 50 ? cout << "NO\n" : cout << "YES\n";
}