#include <iostream>
using namespace std;

int main() {
	long long input = 600851475143;
	long long mx = 0;
	for (int x = 2; x <= input/x; ++x){
		while(input%x==0) {input/=x; mx = x; }
		
	}
	if (input > 1){
		mx = input;
	}
	cout << mx << endl;
	return 0;
}