View Compilation Error

0_0_24805615_22849.cpp: In function 'int main()':
0_0_24805615_22849.cpp:24:8: error: 'cin' was not declared in this scope
  while(cin>>l>>n>>m)
        ^
0_0_24805615_22849.cpp:24:8: note: suggested alternative:
In file included from 0_0_24805615_22849.cpp:1:0:
GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^
0_0_24805615_22849.cpp:39:17: error: 'sort' was not declared in this scope
   sort(ab,ab+num);
                 ^
0_0_24805615_22849.cpp:39:17: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:62:0,
                 from 0_0_24805615_22849.cpp:2:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algo.h:4705:5: note:   'std::sort'
     sort(_RandomAccessIterator __first, _RandomAccessIterator __last,
     ^