# -*- coding: utf-8 -*-
N = input()
temp = [0, 0, 0]
memo = [1, 0, 0]
for i in range(1, N):
    temp[0] = memo[2]
    temp[1] = memo[0]
    temp[2] = memo[0] + memo[1]
    for k in range(0, 3):
        memo[k] = temp[k]
print int(sum(memo) % (10E+9 + 7))