codeup 3704

import sys

sys.setrecursionlimit(60000)

n = int(input())

count = 0
memo = [0 for _ in range(100001)]


def recursive(step):

    if step == 1:
        return 1
    if step == 2:
        return 2
    if step == 3:
        return 4

    if memo[step] != 0 :
        return memo[step]%1000
    else:
        memo[step] = (recursive(step - 3) + recursive(step - 2) + recursive(step - 1))%1000
        return memo[step]


print(recursive(n))