/in/foo.cc:16:37: error: 'bool time' redeclared as different kind of symbol
 bool sg[20000],Map[2000][2000],flag,time;
                                     ^~~~
In file included from /usr/include/pthread.h:24:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/gthr-default.h:35,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/gthr.h:148,
                 from /usr/include/c++/6/ext/atomicity.h:35,
                 from /usr/include/c++/6/bits/ios_base.h:39,
                 from /usr/include/c++/6/ios:42,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:1:
/usr/include/time.h:192:15: note: previous declaration 'time_t time(time_t*)'
 extern time_t time (time_t *__timer) __THROW;
               ^~~~