private fun readLn() = readLine()!!
private fun readStrings() = readLn().split(" ")
private fun readInt() = readLn().toInt()
private fun readInts() = readStrings().map { it.toInt() }
private fun readLong() = readLn().toLong()
private fun readLongs() = readStrings().map { it.toLong() }
private fun readDouble() = readLn().toDouble()
private fun readDoubles() = readStrings().map { it.toDouble() }

fun main(args: Array<String>) {
        val n= readInt()
        if(n>=30)
            println("Yes")
        else
            println("No")
}