#class step:
#	def __init__(self, name, unlocks):
#		self.name = name;
#		self.unlocks = unlocks;


def TransInstr (instruction):
	return [instruction[5], instruction[36]];
	

myinput = {};

currentfilename = "input.txt";
#currentfilename = "testinput.txt";

f = open(currentfilename, 'r');

#list1 = [];
#list2 = {};
list2 = set();

for line in f:
	nowinstr = TransInstr(line);
	#myinput[nowinstr[1]].append(nowinstr[0]);
	list2.add(nowinstr[0]);
	
#'''
	try:
		myinput[nowinstr[1]].append(nowinstr[0]);
		#myinput[nowinstr[1]] = nowinstr[0];
	except:
		myinput[nowinstr[1]] = [];
		myinput[nowinstr[1]].append(nowinstr[0]);
#'''

print(myinput.keys());
print("##############");
print(list2);
print("##############");

pr1 = list(myinput.keys());
pr1.sort();
pr2 = list(list2);
pr2.sort();
print(pr1);
print(pr2);
print("##############");

print("##############");
print("finding the first step");

CurrentStep = '';

AvailableSteps = [];
#AvailableSteps.append(CurrentStep);

for l in list2:
	IsUnique = True;
	for k in myinput.keys():
		#print("L ", l, "\tK ",k, "\t",l == k);
		if (l == k):
			IsUnique = False; 
			break;
	if IsUnique:
		#CurrentStep = l;
		#break;
		AvailableSteps.append(l);
		
print("Unique values are ", AvailableSteps);

print("##############");
print(myinput);
print("##############");
part1 = ""; #CurrentStep;

#list1 = myinput.keys();
#list1.append(CurrentStep);
#print(list1); 


while (len(AvailableSteps) != 0):
	#input();
	AvailableSteps.sort();
	CurrentStep = AvailableSteps[0];
	part1 += CurrentStep;
	print("now ", CurrentStep);
	for step in myinput:
		#x = myinput[step].index(CurrentStep);
		#print(x, "\t",myinput[step]);
		#myinput[step].pop(0);
		#print(x, "\t",myinput[step]);
		try:
			#print("try worked");
			myinput[step].pop(myinput[step].index(CurrentStep));
		except:
			#print("skip");
			pass;
		if (len(myinput[step]) == 0 and part1.find(step) == -1):
			AvailableSteps.append(step);
	
	AvailableSteps.pop(0);

print("##################################");

def RemoveDupsOrder(TheString):
	a = "";
	for letter in TheString:
		if not (letter in a):
			a += letter;
	return a;

print(part1);

part1 = RemoveDupsOrder(part1);

print(part1);