import java.util.PriorityQueue;

import java.util.Comparator;

public class Problem3 {

public static void main(String[] args){

long num = 600851475143L;

long result = 2;

PriorityQueue<Long> q = new PriorityQueue<Long>(1, new Comparator<Long>(){

public int compare(Long arg0, Long arg1) {

return arg0.compareTo(arg1) * -1;

}

});

while( num > 1 ){

while( num % result == 0){

q.offer(result);

num /= result;

}

result += 1;

}

System.out.println(q.poll());

}

public static boolean isPrime(long x){

if(x == 2) return true;

if(x == 3) return true;

if(x < 2) return false;

return ((x % 2 != 0) && (x % 3 != 0));

}

}