Stuff

def getSequence(dominoes):
	for i, dom in enumerate(dominoes):
		ret = isSequence([dom], dominoes[0:i] + dominoes[i+1:])
		if len(ret) > 0:
			return ret

def isSequence (current, available):

	if len(available) == 0:
		return current
	
	for i, option in enumerate(available):
		
		if current[-1][1] == option[0]:
			newSequence = current[:]
			newSequence.append(option)
			ret = isSequence(newSequence, available[0:i] + available[i+1:]) 
			if len(ret) != 0:
				return ret
		
		if current[-1][1] == option[1] :
			newSequence = current[:]
			a = [option[1], option[0]]
			newSequence.append(a)
			ret = isSequence(newSequence, available[0:i] + available[i+1:])
			if len(ret) != 0:
				return ret
				
	return []

s = raw_input()
ps = s.split(' ')
ps.pop(0)
points = []

for elem in ps:
	points.append(elem.split(":"))
	
print getSequence(points)