#include <stdio.h>

int fromhex(int a)
{
	return(a<='9'?a-'0':a-'A'+10);
}

int main(int argc,char **argv)
{
char c,seek;
int i;
	if (argc>1&&*(argv[1])) seek=*(argv[1]);
	for (;;) {
		i=getchar();
		if (i==-1) break;
		if (i!=seek) { putchar(i); continue; }
		i=getchar();
		if (i=='\n') continue;
		if (i==-1) break;
		c=i;
		i=getchar();
		if (i==-1) break;
		putchar(fromhex(c)*0x10+fromhex(i));
		}
	return(0);
}