#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from functools import reduce

CHAR_TO_INT = {
    '0': 0,
    '1': 1,
    '2': 2,
    '3': 3,
    '4': 4,
    '5': 5,
    '6': 6,
    '7': 7,
    '8': 8,
    '9': 9
}

def str2int(s):
    ints = map(lambda ch: CHAR_TO_INT[ch], s)
    return reduce(lambda x, y: x * 10 + y, ints)

print(str2int('0'))
print(str2int('12300'))
print(str2int('0012345'))