题解 | #汽水瓶#

 #include <bits/stdc++.h>
using namespace std;

int main(){
  int i;
  int count;

  while(cin>>i){
      if(i==0) return 0;

      count=0;
      while(i>=2){
          if(i>=3){
              count+=i/3;
              i=i%3+i/3;
          }else{
              count++;
              i=0;
          }
      }
      cout<<count<<endl;
  }
  return 0;
}