View Compilation Error

0_0_16343029_22840.cpp: In function 'int solve()':
0_0_16343029_22840.cpp:41:22: error: 'sort' was not declared in this scope
  sort( S , S+n , cmp ) ;
                      ^
0_0_16343029_22840.cpp:41:22: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:62:0,
                 from 0_0_16343029_22840.cpp:5:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algo.h:4705:5: note:   'std::sort'
     sort(_RandomAccessIterator __first, _RandomAccessIterator __last,
     ^