from pwn import * 
from ctypes import * 

p = process('./chall_17')
binary = ELF('./chall_17')

# get right library
lib_c = cdll.LoadLibrary('libc.so.6')
lib_c = srand(c_lib.time(None))

p.sendline(str(lib_c.rand()))
print(p.recvuntil('\n'))