It's trivial when we notice that with c1=1 the program simply accepts the message from c2.
We put c1=1 and c2="something#overlord" and we get the flag.
```
#!/usr/bin/env python2

from pwn import *
import binascii

p = remote("35.197.255.108", "1337")
p.sendline("1")
p.sendline("1" + binascii.hexlify("easy#overlord"))
print(p.recvuntil("here."))*
```