import java.util.Scanner;
 
 public class largestprimenumber {
    
    public static void main(String[] args) {
    	Scanner s = new Scanner(System.in);
    	System.out.print("Enter number: ");
    	long number = s.nextLong();
    	long answer = calculate(number);
    	System.out.println("Largest Prime factor is " + answer);
    }
    public static long calculate(long n) {
    	long k = 0;
    	long l = (long)Math.sqrt(n);
    	for(long i = 1; i <= l; i++) {
    		if((n % i == 0) && isPrime(i))
    			k = i;
    	}
    	return k;
    }
    
    public static boolean isPrime(long n) {
    	for (long i = 2; i < n; i++) {
    		if(n % i == 0)
    			return false;
    	}
    	return true;
    }
}