/in/foo.cc:5:1: error: 'priority_queue' does not name a type
 priority_queue<int> app, tt;
 ^~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:8:2: error: 'cin' was not declared in this scope
  cin >> n >> m;
  ^~~
/in/foo.cc:8:2: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
/in/foo.cc:13:3: error: 'app' was not declared in this scope
   app.push(tmp);
   ^~~
/in/foo.cc:18:3: error: 'tt' was not declared in this scope
   tt.push(tmp);
   ^~
/in/foo.cc:21:10: error: 'app' was not declared in this scope
  while (!app.empty() && !tt.empty()) {
          ^~~
/in/foo.cc:21:26: error: 'tt' was not declared in this scope
  while (!app.empty() && !tt.empty()) {
                          ^~