def base36_to_int(s):
    return int(s, 36)

def int_to_base36(i):
    digits = "0123456789abcdefghijklmnopqrstuvwxyz"
    factor = 0
    # Find starting factor
    while True:
        factor += 1
        if i < 36 ** factor:
            factor -= 1
            break
    base36 = []
    # Construct base36 representation
    while factor >= 0:
        j = 36 ** factor
        base36.append(digits[i / j])
        i = i % j
        factor -= 1
    return ''.join(base36)