Problem:
Euler's Phi Function

For given integer n, count the totatives of n, that is, the positive integers less than or equal to n that are relatively prime to n.

Input

n

An integer n (1 ≤ n ≤ 1000000000).

Output

The number of totatives in a line.

Sample Input 1

6

Sample Output 1

2

Sample Input 2

1000000

Sample Output 2

400000

Solution in JAVA (judge verdict: Accepted)

import java.util.Scanner;
 
public class Main {
     
     
     
    public static void main(String args[]){
        try(Scanner sc=new Scanner(System.in)){
            int n=sc.nextInt();
            int x=n;
            int count=n;
            for(int i=2; i*i<=x; i++) {
                if(n%i==0) {
                    count-=count/i;
                    while(n%i==0) {
                        n/=i;
                    }
                }
            }
            if(n>1) {
                count-=count/n;
            }
            System.out.println(count);
        }
    }
}