/* -*- coding: utf-8 -*-
 *
 * 2140.cc:  No.2140 Triangle - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  // a<b+x,b<a+x,x<a+b,a<=b -> 0<=b-a<x<b+a

  int a;
  scanf("%d", &a);
  printf("%d\n", a * 2 - 1);
  return 0;
}