# -*- coding: utf-8 -*-
"""
No.44 DPなすごろく
https://yukicoder.me/problems/no/44

"""
import sys
from sys import stdin

input = stdin.readline


def solve(n):
    dp = [[0] * (n+1) for _ in range(n+1)]
    dp[0][0] = 1

    for i in range(1, n+1):
        for j in range(i, n+1):
            t = 0
            for k in range(1, 2+1):
                if j-k < 0:
                    continue
                t += dp[i-1][j-k]
            dp[i][j] = t

    total = 0
    for d in dp:
        total += d[-1]
    return total


def main(args):
    n = int(input())

    ans = solve(n)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])