solve.py

#!/usr/bin/env python

# t: flag[i]
# check(t^0x7f, i, c_flag)
#
# def check(c, i, c_flag):
#   return bc + 2239 * c == c_flag[i]
#   ( bc = c )

# c = (c_flag[i] - bc) / 2239

c_flag = [ 0x20405, 0x1a40b, 0x16f86, 0x215ad, 0x1be4a, 0x1fb79, 0x1181a, 0x1c6ec, 0x1fb7a, 0x1d884, 0x1810a, 0x16f82, 0x1c6f6, 0x1fb7a ]

bc = 0

def solvec(i):
  global bc
  ret = (c_flag[i] - bc) / 2239
  bc = ret
  return ret

flag = ''
for i in range(len(c_flag)):
  c = solvec(i) ^ 0x7f
  flag += chr(c)

print flag