# -*- coding: utf-8 -*-
import time
N = input()
memo = [1L, 0L, 0L]
cnt = 1
while cnt < N:
    memo[0], memo[1], memo[2] = memo[2] % 1000000007, memo[0] % 1000000007, (memo[0] + memo[1]) % 1000000007
    cnt += 1
print sum(memo) % 1000000007