func readInt() -> Int {
    Int(readLine()!)!
}
 
func readInts() -> [Int] {
    readLine()!.split(separator: " ").map { Int($0)! }
}
 
prefix operator *
prefix func * <T> (a: [T]) -> (T, T) {return (a[0], a[1])}
prefix func * <T> (a: [T]) -> (T, T, T) {return (a[0], a[1], a[2])}

let x = readInt()

print(x >= 30 ? "Yes" : "No")