S=input()
T=input()
if(0<=len(S)-len(T)<=1):
	if(len(S)>len(T)):
		for i in range(len(T)):
			print(S[i],end="")
			print(T[i],end="")
		print(S[-1])
	else:
		for i in range(len(S)):
			print(S[i],end="")
			print(T[i],end="")
		print()
else:
	print("?")