import java.util.*;
import java.io.*;
 
class Main{
    public static final int INF = Integer.MAX_VALUE;
    public static PrintWriter out = new PrintWriter(System.out);
    public static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws IOException {
        int A = sc.nextInt();
        long ans = 0;
        //必要条件 a + b > c || a + c > b
        //A == B のとき
        ans += (A*2)-1;
        out.print(ans);
        out.flush();
    }
}