AtCoder. ABC 238 A Exponential or Quadratic

Problem: AtCoder ABC 238 A — Exponential or Quadratic [English] · 한국어 · 日本語

We need to determine whether 2^N > N^2. There is no need to calculate the power: for N = 1, the inequality holds; for N = 2, 3, 4, it does not (2^4 = 4^2). Starting at N = 5, it is always true. If 2^N > N^2 for some N >= 5, then 2^(N + 1) > 2N^2 >= (N + 1)^2, so the inequality continues to hold for every larger integer.

Therefore, the answer is Yes exactly when N = 1 or N >= 5; otherwise it is No. A pair of integer comparisons is enough, even for large permitted values of N.

Java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(input.readLine().trim());
        System.out.println(n == 1 || n >= 5 ? "Yes" : "No");
    }
}