#include<string>
#include<cmath>

using namespace std;


int main() {

    cout << "enter the number: ";
    string s;

    bool x = true;

    while (x)
    {
        getline(cin, s);
        x = false;

        for (int i = 0; i < s.size(); i++)
        {
            if (s[i] != 48 && s[i] != 49)
            {
                cout << "inavalid input, try again:";
                s.clear();
                x = true;
            }
        }
    }

    long long int dec = 0;
    int count = 0;

    for (int i = s.length() - 1; i > 0; i--)
    {
        if (s[0] = 1)
        {
            if (s[i] == 0)
            {
                s[i] = 1;
            }
            else
            {
                s[i] = 0;
            }
            dec += pow(2, count) * (s[i] - '0');
            count++;
        }
        else {
            dec += pow(2, count) * (s[i] - '0');
            count++;
        }
    }

    if (s[0] == 1)
    {
        cout << endl << - dec;
    }
    else
    {
        cout << endl << dec;
    }


    return 0;
}