first_string = str(input()) second_string = str(input()) first_list = [] second_list = [] for index in range(0, len(first_string)): first_list.append(first_string[index]) second_list.append(second_string[index]) for xedni in range(0, len(first_string)): if first_list[xedni] == second_list[xedni]: continue else: first_list[xedni] = second_list[xedni] print(*first_list, sep="")