Simple script to run this, just do not count 0 as the first number but 1.
```pyfrom pwn import *
r = remote("challs.n00bzunit3d.xyz", 13541)
for _ in range(100):    r.recvuntil(b"How many ")    num = int(r.recv(1).decode('utf-8'))    r.recvuntil(b"appear till ")    num2 = int(r.recv().decode('utf-8').replace('?\n',''))    a = 0    for i in range(num2):        a += str(i).count(str(num))    if num == 0:        a -= 1    r.sendline(bytes(str(a),'utf-8'))
print(r.recv())```
Flag: `n00bz{4n_345y_pr0gr4mm1ng_ch4ll}`