#include <bits/stdc++.h>
using namespace std;
int main(){
	int a,s;
	cin>>a;
	if(a%2==0){
		s=a+1;
	}
	if(a%2!=0){
		s=a/2+1;
	}cout<<s;
}

/**************************************************************
	Problem: 1558
	User: tonghuawei
	Language: C++
	Result: Accepted
	Time:57 ms
	Memory:2072 kb
****************************************************************/