// BISMILLAH

#include "bits/stdc++.h"

#define fastIO std::ios::sync_with_stdio(0);std::cin.tie(0)
#define ll long long int
#define flush fflush(stdout)
// #define int ll

using pii = std::pair<int,int>;

const int MOD = 1000000007;
// const int MOD = 998244353;
const int mxN = 500005, inf = 1000000005;

signed main() {
	// fastIO;
	int testCases=1;
	// scanf("%lld",&testCases);
	// std::cin >> testCases;
	
	for (int T = 1; T <= testCases; T++) {
        int x;
        scanf("%d", &x);
        printf("%s\n", x <= 50 ? "YES" : "NO");
    }
	
	return 0;
}

/*

*/