#pragma once

#define isspace_fast(x) ((x) == ' ' || (x) == '\t' || (x) == '\n' || (x) == '\v' || (x) == '\f' || (x) == '\r')

int fast_atoi(const char *b)
{
    int res = 0; // Initialize result

    // Skip whitespace
    for (; isspace_fast(*b); ++b);

    if (*b == '-')
    {
        ++b;
        // Iterate through all characters of input string and update result
        for (; ; ++b)
        {
            unsigned d = static_cast<unsigned>(*b) - '0';
            if (d > 9) 
            {
                return res;
            }
            res = res * 10 - d;
        }

    } 
    else if (*b == '+')
    {
        ++b;
    }
    
    // Iterate through all characters of input string and update result
    for (; ; ++b)
    {
        unsigned d = static_cast<unsigned>(*b) - '0';
        if (d > 9) 
        {
            return res;
        }
        res = res * 10 + d;
    }

    //  unreachable
    return res;
}