#!/usr/bin/python

# just a dirty unbuffered getch()
import sys, tty, termios
def raw_getch():
    setbak = termios.tcgetattr(sys.stdin.fileno())
    try:
        tty.setraw(sys.stdin.fileno())
        ch = sys.stdin.read(1)
    finally:
        termios.tcsetattr(sys.stdin.fileno(), termios.TCSADRAIN, setbak)
    return ch

# binary keyboard, use u and d keys to select the line
def bin_select(chars):
    while len(chars) > 1:
        upper = chars[0:len(chars)/2]
        lower = chars[len(chars)/2:len(chars)]
        print ''.join(upper)
        print ''.join(lower)

        inp = raw_getch()
        if inp == 'u':
            chars = upper
        elif inp == 'd':
            chars = lower

    return chars[0]

if __name__ == '__main__':
    chars = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
             'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '0', '1',
             '2', '3', '4', '5', '6', '7', '8', '9', '.', ',', '-', '_']
    print bin_select(chars)