#!/usr/bin/env python
# coding: utf-8

# In[21]:


import hashlib

def mine(key, zeros=5):
    key = key.encode()
    n = 0
    z = '0' * zeros
    while True:
        n += 1
        nb = str(n).encode()
        hex = hashlib.md5(key + nb).hexdigest()
        if hex.startswith(z):
            return n


# In[22]:


assert mine('abcdef', 5) == 609043
assert mine('pqrstuv', 5) == 1048970


# In[23]:


mine('yzbqklnj', 5)


# In[24]:


mine('yzbqklnj', 6)