View Compilation Error

0_0_30517413_4525.cpp: In function 'int main()':
0_0_30517413_4525.cpp:42:21: error: 'sort' was not declared in this scope
   sort(a, a + n, cmp);
                     ^
0_0_30517413_4525.cpp:42:21: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:62:0,
                 from 0_0_30517413_4525.cpp:3:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algo.h:4705:5: note:   'std::sort'
     sort(_RandomAccessIterator __first, _RandomAccessIterator __last,
     ^
0_0_30517413_4525.cpp:45:61: error: 'max' was not declared in this scope
    printf("%lld\n", max((a[0].x + b[1].x), (a[1].x + b[0].x)));
                                                             ^
0_0_30517413_4525.cpp:45:61: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:62:0,
                 from 0_0_30517413_4525.cpp:3:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algo.h:3454:5: note:   'std::max'
     max(initializer_list<_Tp> __l, _Compare __comp)
     ^