/in/foo.cc: In function 'int main()':
/in/foo.cc:7:9: warning: unused variable 'xh' [-Wunused-variable]
     int xh;                          //序  号
         ^~
/in/foo.cc:29:13: warning: 'tt' may be used uninitialized in this function [-Wmaybe-uninitialized]
     cout<<tt;
             ^