import hashlib

def check(data, proof, complexity=1, f=hashlib.sha256):
    zeros="0"*complexity
    hash=f((str(proof)+data).encode())
    hashdata=hash.hexdigest()
    b=0
    for a in hashdata:
        if a=="0":
            b+=1
        else:
            break
    return b>=complexity

def mine(data, complexity=1, f=hashlib.sha256):
    for a in range(0, 1000000000):
        if check(data, a, complexity, f):
            return a
            break