hdoj_2018

#include<stdio.h>
int main(){
    int n,i,a[60];
    a[1]=1,a[2]=2,a[3]=3;
    for(i=4;i<55;i++){
        a[i]=a[i-1]+a[i-3];
    }
//  while(scanf("%d",&n),n){
    while(scanf("%d",&n)!=EOF){
            if(n==0) {
            continue;}
            printf("%d\n",a[n]);
        }
    return 0;
}