Pieces

My flag has been divided into pieces :( Can you recover it for me?

Files

• Main.java

Solution

The divide function in the given code replaces each character ch in the parameter string with two other characters:

• The character whose ASCII is half (integer division) of the ASCII of ch.

• ’	’ if ASCII of ch is even and ‘/’ otherwise.

The flag will be printed if the input to divide results in the string "9|2/9/:|4/7|8|4/2/1/2/9/", we just have to reverse the divide function with this string as the parameter to get the input/flag.

str='9|2/9/:|4/7|8|4/2/1/2/9/'
idx = 0
ans  = ''

while idx < len(str):
    a = ord(str[idx])
    if str[idx+1] == '|':
        ans += chr(a*2) # the original characters ASCII is even
    else:
        ans += chr(a*2 + 1) # the original characters ASCII is odd
    idx += 2

print('rgbCTF{' + ans + '}')

Flag

rgbCTF{restinpieces}