#include <stdio.h>
#include <string.h>
#include <stdbool.h>

void usage()
{
        printf("Provide string number(only 0-9 and '-' sign) to parse into integer!\n");
}

int toInt(const char c) {
        if(c > '9' || c < '0')
                return -1;
        return c - '0';
}

int main(int argc, char** argv)
{
        if (argc < 2) {
                usage();
                return -1;
        }

        bool minus = argv[1][0] == '-';
        printf("Minus: %s\n", minus == true ? "true" : "false");

        int number = 0;
        int len = strlen(argv[1]);

        printf("Len %d\n", len);

        for (int i = minus ? 1 : 0; i < len; i++) {
                int num = toInt(argv[1][i]);

                if (num == -1) {
                        usage();
                        return -2;
                }

                number = number * 10 + num;
        }

        if (minus) {
                number *= -1;
        }

        printf("input: %s, numer: %d\n", argv[1], number);

return 0;
}