# from https://www.askpython.com/python/examples/possible-subsequences-subsets
def get_all_subsequence(n, output, i):
if (i == len(n)):
if (len(output) != 0):
print(output)
else:
# exclude first character
get_all_subsequence(n, output, i + 1)
# include first character
output += n[i]
get_all_subsequence(n, output, i + 1)
return
n = input()
get_all_subsequence(n, "", 0)
print(n[0])