#include <bits/stdc++.h>
using namespace std;
 
int main() {
  int x, y;
  cin >> x >> y;
  int A=x-y;
  if(A%2==1){
  	if(x>=0 && y>=0){
  		cout<< x+y<<endl;
  	}
  	if(x>=0 && y<0){
  		cout<< x-y << endl;
  	}
  	if(x<0 && y>=0){
  		cout<< y-x <<endl;
  	}
  	else{
  		cout<<0-y-x <<endl;
  	}
  }
  else{
	if(x>=0 && y>=0){
  		if(x>=y){
  			cout<< x <<endl;
  		}
  		else{
  			cout<<y<<endl;
  		}
  	}
  	if(x>=0 && y<0){
  		if(x>=0-y){
  			cout<< x <<endl;
  		}
  		else{
  			cout<<0-y<<endl;
  		}
  	}
  	if(x<0 && y>=0){
  		if(0-x>=y){
  			cout<< 0-x <<endl;
  		}
  		else{
  			cout<<y<<endl;
  		}
  	}
  	else{
  		if(x>=y){
  			cout<< 0-y <<endl;
  		}
  		else{
  			cout<<0-x<<endl;
  		}
  	}
  }
}