#include<iostream>
using namespace std;
int main(){
    int a,b:
    cin>>a>>b;
    if(a<0||b<0){
        cout<<"invalid"<<endl;
        return 0;
    }
    if(a%2==0 && b%2==0){
        cout<<a*b<<endl;
    }
    else if(a%2!=0 && b%2!=0){
        cout<<a+b;
        
    }
    else{
        cout<<abs(a-b);
    }
    return 0;
    
}