/in/foo.cc: In function 'int bianhuan(int)':
/in/foo.cc:29:2: error: expected ';' before 'return'
  return bianhuan(t);
  ^~~~~~
/in/foo.cc:29:20: warning: statement has no effect [-Wunused-value]
  return bianhuan(t);
                    ^
/in/foo.cc:30:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^