#include <iostream>
#include <fstream>

using namespace std;

int main () {

    ifstream fin("cmmdc.in");
    ofstream fout("cmmdc.out");

    int a,b,d,e;

    d=a-b;
    e=b-a;
    fin>>a>>b;

    if(a%b==0) {

        fout << 0;
    }
        else
        if(a!=b) {
           fout<< d;
        }
        else
            if(b!=a)
            fout << e;

    fin.close();
    fout.close();

}