#include<bits/stdc++.h>
using namespace std;

#define INF 1234567890
#define ll long long

int N;

int main()
{
	ios::sync_with_stdio(0); cin.tie(0);
	cin.exceptions(ios::badbit | ios::failbit);
	cin >> N;
	cout << N+N-1 << "\n";
	return 0;
}