#include<stdio.h>
//递归 
 int sum(int n)
{
    if (n <= 4) return n;
    else return (sum(n-1) + sum(n - 3));
}
int main()
{
    int n;
    while (~scanf("%d", &n) != EOF&&n!=0)
        printf("%d\n", sum(n));
    getchar();
    return 0;
}
#include<stdio.h>
//迭代 
int main()
{
    int f1,f2,f3,fn,i,n;
    while(~scanf("%d",&n)&&n!=0)
    {
        if(n==1)fn=1;
        else if(n==2)fn=2;
        else if(n==3)fn=3;
        else
        {
            f1=1;
            f2=2;
            f3=3;
            for(i=4;i<=n;i++)
            {
                fn=f1+f3;
                f1=f2;       
                f2=f3;
                f3=fn;    
            }
        }    
        printf("%d\n",fn);
    }
    return 0;
 }