'''
Created on Apr 23, 2019

@author: facebook
'''
#def f(x): 
 #   a = [] 
 #   for i in x: 
 #       if i not in a: 
 #           a.append(i) 
#return a 

#x = [2,4,10,20,5,2,20,4] 
#print(f(x)) 
        

x = 'facebook'
z = []
for i in x:
    if i not in z:
        z.append(i)
        print z
        