<?php
// yukicoder My Practice
// author: Leonardone @ NEETSDKASU

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

$n = intval(fgets(STDIN));

$a = $c = 0; $b = 1;

while (--$n > 0) {
    $ta = ($b + $c) % 1000000007;
    $c = $b; $b = $a; $a = $ta;
}

$r = ($a + $b + $c) % 1000000007;
echo "{$r}", PHP_EOL;