import java.util.Scanner;

import com.sun.org.apache.bcel.internal.generic.IREM;

public class Main {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		if (n==1) {
			System.out.println(1);
		}else if (n==2) {
			System.out.println(2);
		}else if (n==3) {
			System.out.println(4);
		}else {
			long []array = new long[n+1];
			array[1]=1;
			array[2]=2;
			array[3]=4;
			for (int i = 4; i <= n; i++) {
				array[i]=(array[i-1]+array[i-2]+array[i-3])%1000000007;
			}
		}
	}
}