#!/bin/bash

# yukicoder My Practice
# author: Leonardone @ NEETSDKASU

# 解説読後
# http://yukicoder.me/problems/882/editorial

typeset -i n a b c t

mapfile -t n

a=0
b=1
c=0

for ((n=$n-1;$n;n--)); do {
    t=$(((b+c) % 1000000007));
    c=$b;
    b=$a;
    a=$t;
}; done;

t=$(((a+b+c) % 1000000007))

echo $t