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

#define deb(x) cout << #x << " " << x << "\n";
#define fo(i, n) for(i=0; i<n; i++)
#define Fo(i, k, n) for(i=k; i<n; i++)
#define endl "\n"
#define ll long long
#define vi vector<int>

// memset(arr, value, size);

int main() {
#ifndef ONLINE_JUDGE
	freopen("input1.txt", "r", stdin);
	freopen("output1.txt", "w", stdout);
#endif
	ios::sync_with_stdio(0);
	cin.tie(0);

	int t;
	cin >> t;
	cout << (t >= 30 ? "YES" : "NO");

	return 0;
}