#include<stdio.h>

int main(){

int n;

while(1)

{

scanf("%d",&n);

if(n==0){break;}

int a1=0,a2=0,a3=1,b1,b2,b3;

for(int i=2;i<=n;i++){

b1=a1;

b2=a2;

b3=a3;

a1=b3;

a2=b1;

a3=a3+b2;

}

printf("%d\n",a1+a2+a3);

}

return 0;

}