/in/foo.cc: In function 'int main()':
/in/foo.cc:13:10: warning: unused variable 'j' [-Wunused-variable]
  int i=0,j=0,fb;//fb:第二个操作数的符号
          ^
/in/foo.cc:14:7: warning: unused variable 'f' [-Wunused-variable]
  bool f=true,end=false;
       ^
/in/foo.cc:45:6: warning: unused variable 'temp' [-Wunused-variable]
  int temp=0;
      ^~~~