/in/foo.cc: In function 'int main()':
/in/foo.cc:12:6: warning: unused variable 'jian' [-Wunused-variable]
  int jian,maxj=0;
      ^~~~
/in/foo.cc:22:17: warning: 'b1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<a1<<" "<<b1<<endl;
                 ^~
/in/foo.cc:22:12: warning: 'a1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<a1<<" "<<b1<<endl;
            ^~~