int char_to_int(char a) {
        const char nums[] = "0123456789";

        for(int i=0; i < 10; ++i) {
                if (nums[i] == a) {
                        return i;
                }
        }

        return 0;
}

char int_to_char(int n) {
        const char nums[] = "0123456789";

        if (n < 0 || n > 9) {
                return 0;
        }

        return nums[n];
}