Solution.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

  // Complete the viralAdvertising function below.
  static int viralAdvertising(int n) {
    int total = 2;
    int[] day = new int[n];
    day[0] = 2;
    for (int i = 1; i < n; i++) {
      day[i] = day[i - 1] * 3 / 2;
      total += day[i];
    }
    return total;
  }

  private static final Scanner scanner = new Scanner(System.in);

  public static void main(String[] args) throws IOException {
    BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

    int n = scanner.nextInt();
    scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

    int result = viralAdvertising(n);

    bufferedWriter.write(String.valueOf(result));
    bufferedWriter.newLine();

    bufferedWriter.close();

    scanner.close();
  }
}