#include <iostream>
#define N 1000000
using namespace std;
int dp[N];        
int fun(int n)    
{
 if(n<=3)
 {
  dp[1]= 1;
  dp[2]= 2;
  dp[3]= 4;
 }
 else
  dp[n] = ((dp[n-1]+dp[n-2])% 1000000007+dp[n-3])% 1000000007;
  
 return dp[n];
}

int main()
{
 int n;
 cin>>n;
  for(int i=1;i<=n;i++)
   fun(i);
 cout<<dp[n]<<endl; 
 
}