char low(char c)
{
    if (c >= 'A' && c <= 'Z')
    {
        return 'a' + (c - 'A');
    }
    else
    {
        return c;
    }
}

char high(char c)
{
    if (c >= 'a' && c <= 'z')
    {
        return 'A' + (c - 'a');
    }
    else return c;
}