/in/foo.cc:1:19: warning: extra tokens at end of #include directive
 #include<iostream>;
                   ^
/in/foo.cc:2:17: warning: extra tokens at end of #include directive
 #include<cstdio>;
                 ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:6:2: error: 'cin' was not declared in this scope
  cin>>n>>k>>a>>b;
  ^~~
/in/foo.cc:6:2: 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:12:15: error: array must be initialized with a brace-enclosed initializer
  bool flag[n]=false;
               ^~~~~
/in/foo.cc:50:2: error: 'cout' was not declared in this scope
  cout<<l<<endl;
  ^~~~
/in/foo.cc:50:2: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
/in/foo.cc:50:11: error: 'endl' was not declared in this scope
  cout<<l<<endl;
           ^~~~
/in/foo.cc:50:11: note: suggested alternative:
In file included from /usr/include/c++/6/iostream:39:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~