这段程序里first的理解。

#include<iostream>
using namespace::std;
int main(){
   char first,second;
   int ffcnt=0,flcnt=0,ficnt=0;
   while(cin>>second){
       if(first=='f'){
           switch(second){
               case 'f':
               ++ffcnt;
               break;
               case 'l':
               ++flcnt;
               break;
               case'i':
               ++ficnt;
               break;
         }
           }first=second ;
   
   }
    cout<<"ff is "<<ffcnt<<endl;
    cout<<"fl is "<<flcnt<<endl;
    cout<<"fi is "<<ficnt<<endl;

    return 0;
}