//ADUNARE PRIN BACKTRACKING
//MADE BY BIGFOOT

#include <fstream>

using namespace std;

ifstream f("adunare.in");
ofstream g("adunare.out");

long s1, s2, a, b;
bool v1, v2;

int main()
{
    f >> a >> b;
    s1 = s2 = 0;
    while (v1 == false && v2 == false)
    {
        s1--;
        if (s1 - a == b && s1 - b == a)
            v1 = true;
        s2++;
        if (s2 - a == b && s2 - b == a)
            v2 = true;
    }
    if (v1 == true)
        g << s1;
    else if (v2 == true)
        g << s2;
}