test.c

#include <stdio.h>
#include <stdlib.h>
char *serial = "\x31\x3e\x3d\x26\x31";
int check(char *ptr)
{
	int i;
	int hash = 0xABCD;
	for (i = 0; ptr[i]; i++)
		hash += ptr[i] ^ serial[i % 5];
	return hash;
}
int main(int ac, char **av)
{
	int ret;
	if (ac != 2)
		return -1;
	ret = check(av[1]);
	if (ret == 0xad6d)
		printf("Win\n");
	else
		printf("fail\n");
	return 0;
}