/in/foo.cc: In function 'int main()':
/in/foo.cc:14:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define For(i,j,k) for(int i=j;i<=k;i++)
                                  
/in/foo.cc:28:6:
  For(i,2,s.length()-2)
      ~~~~~~~~~~~~~~~~            
/in/foo.cc:28:2: note: in expansion of macro 'For'
  For(i,2,s.length()-2)
  ^~~
/in/foo.cc:14:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define For(i,j,k) for(int i=j;i<=k;i++)
                                  
/in/foo.cc:37:6:
  For(i,bj+1,s.length()-2)
      ~~~~~~~~~~~~~~~~~~~         
/in/foo.cc:37:2: note: in expansion of macro 'For'
  For(i,bj+1,s.length()-2)
  ^~~
/in/foo.cc:27:6: warning: unused variable 'len' [-Wunused-variable]
  int len=s.length();
      ^~~