/in/foo.cc:2:7: error: expected nested-name-specifier before 'namespaces'
 using namespaces std;
       ^~~~~~~~~~
/in/foo.cc:5:23: error: expected unqualified-id before '=' token
 const int maxn=1e3+10;=
                       ^
/in/foo.cc:9:2: error: 'a' does not name a type
 }a[maxn];
  ^
/in/foo.cc: In function 'void px()':
/in/foo.cc:13:23: error: expected ';' before ')' token
      for(int j=i+1;j++)
                       ^
/in/foo.cc:14:9: error: 'a' was not declared in this scope
      if(a[i].y<a[j],y) swap(a[i],a[j]);
         ^
/in/foo.cc:14:21: error: 'y' was not declared in this scope
      if(a[i].y<a[j],y) swap(a[i],a[j]);
                     ^
/in/foo.cc:14:38: error: 'swap' was not declared in this scope
      if(a[i].y<a[j],y) swap(a[i],a[j]);
                                      ^
/in/foo.cc:14:38: note: suggested alternatives:
In file included from /usr/include/c++/6/complex:45:0,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/sstream:783:5: note:   'std::__cxx11::swap'
     swap(basic_stringbuf<_CharT, _Traits, _Allocator>& __x,
     ^~~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1958:5: note:   'std::__cxx11::swap'
     swap(match_results<_Bi_iter, _Alloc>& __lhs,
     ^~~~
In file included from /usr/include/c++/6/exception:172:0,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/exception_ptr.h:164:5: note:   'std::__exception_ptr::swap'
     swap(exception_ptr& __lhs, exception_ptr& __rhs)
     ^~~~
In file included from /usr/include/c++/6/bits/nested_exception.h:40:0,
                 from /usr/include/c++/6/exception:173,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/move.h:179:5: note:   'std::swap'
     swap(_Tp& __a, _Tp& __b)
     ^~~~
/in/foo.cc: In function 'void init()':
/in/foo.cc:18:2: error: 'cin' was not declared in this scope
  cin>>n;
  ^~~
/in/foo.cc:18:2: note: suggested alternative:
In file included from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:75:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
/in/foo.cc:21:8: error: 'a' was not declared in this scope
   cin>>a[i].y;
        ^