#include<cstdio>


int main(void)
{
	char s[3][10];

	while(scanf("%s%s%s", s[0], s[1], s[2])==3)
	{
		if(s[0][0]==s[1][0] || s[0][0]==s[2][0]) printf("%s\n", s[0]);
		else printf("%s\n", s[1]);
	}

	return 0;
}