[JAVA][Baekjoon] 11689번 GCD(n, k) = 1 🌟🌟

import java.io.*;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        long n = Long.parseLong(br.readLine());
        long result = n;
        for(long p = 2; p<=Math.sqrt(n); p++) {
            if(n%p == 0) {
                result = result - result/p;
                while(n%p == 0) {
                    n/=p;
                }
            }
        }
        if(n>1) result = result - result/n;
        System.out.println(result);
    }
}