#include<iostream>
#include<cmath>
using namespace std;

int main(){
    int A,B;
    cin>>A>>B;
    
    if(A<0 || B>0){
        cout<<"Invalid input";
        
    }
    else if(A%2 = 0 && B%2 = 0){
        cout<<A*B;
    }
     else if(A%2 != 0 && B%2 != 0){
        cout<<A+B;
    }
    else{
        cout<<A-B;
    }
    return 0;
}