/in/foo.cc:8:20: error: 'int select' redeclared as different kind of symbol
 int sys[22],sysn=1,select;
                    ^~~~~~
In file included from /usr/include/x86_64-linux-gnu/sys/types.h:219:0,
                 from /usr/include/stdlib.h:275,
                 from /usr/include/c++/6/cstdlib:75,
                 from /usr/include/c++/6/ext/string_conversions.h:41,
                 from /usr/include/c++/6/bits/basic_string.h:5417,
                 from /usr/include/c++/6/string:52,
                 from /usr/include/c++/6/bits/locale_classes.h:40,
                 from /usr/include/c++/6/bits/ios_base.h:41,
                 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/x86_64-linux-gnu/sys/select.h:108:12: note: previous declaration 'int select(int, fd_set*, fd_set*, fd_set*, timeval*)'
 extern int select (int __nfds, fd_set *__restrict __readfds,
            ^~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:15:21: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  while(temp=getchar())
                     ^
/in/foo.cc:14:6: warning: unused variable 'n' [-Wunused-variable]
  int n,cnt=0;
      ^