/*
 The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ?
*/

#include <stdio.h>

char is_prime(unsigned long long int n) {
	for (unsigned long long int i = 2; i < n; i++) {
		if (n % i == 0) {
			return 0;
		}
	}
	return 1;
}

int main() {
	unsigned long long int c = 600851475143;
	for (unsigned long long int i = c / 2; i--; i >= 0) {
		printf("%llu\n", i);
		if (is_prime(i)) {
			printf("%llu\n", i);
			break;
		}
	}
}