#include<stdio.h>
int getTotalCount(int monthCount)
    {
        int count ;
        if(monthCount>=4){
            count = getTotalCount(monthCount-1)+getTotalCount(monthCount-2);
        }else if(monthCount==3){
            count = 2;
        }else {
            count =1;
        }
        return count;
    }
    
int main()
{
	int n;
	scanf("%d",&n);
	printf("%d",getTotalCount(n));
 } 
    
  
/**************************************************************
	Problem: 1238
	User: admin
	Language: C
	Result: Accepted
	Time:20 ms
	Memory:1144 kb
****************************************************************/