#include <iostream>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <algorithm>
typedef long long LL;
using namespace std;
int main()
{
    LL i,n,a[10005];
    a[1]=1;
    a[2]=2;
    a[3]=3;
    for (i=4;i<10005;i++)
    a[i]=a[i-1]+a[i-3];
    while (cin>>n&&n)
    cout<<a[n]<<endl;
    return 0;
}