View Compilation Error

0_0_16345071_9336.cpp: In function 'int main()':
0_0_16345071_9336.cpp:22:30: error: 'max' was not declared in this scope
             ans=max(f(l),f(r));
                              ^
0_0_16345071_9336.cpp:22:30: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/char_traits.h:39:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ios:40,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ostream:38,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:39,
                 from 0_0_16345071_9336.cpp:1:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algobase.h:261:5: note:   'std::max'
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^
0_0_16345071_9336.cpp:27:30: error: 'max' was not declared in this scope
             ans=max(f(l),f(r));
                              ^
0_0_16345071_9336.cpp:27:30: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/char_traits.h:39:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ios:40,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ostream:38,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:39,
                 from 0_0_16345071_9336.cpp:1:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algobase.h:261:5: note:   'std::max'
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^
0_0_16345071_9336.cpp:32:34: error: 'max' was not declared in this scope
                 ans=max(f(l),f(r));
                                  ^
0_0_16345071_9336.cpp:32:34: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/char_traits.h:39:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ios:40,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ostream:38,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:39,
                 from 0_0_16345071_9336.cpp:1:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algobase.h:261:5: note:   'std::max'
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^
0_0_16345071_9336.cpp:37:34: error: 'max' was not declared in this scope
                 ans=max(f(l),f(r));
                                  ^
0_0_16345071_9336.cpp:37:34: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/char_traits.h:39:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ios:40,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ostream:38,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:39,
                 from 0_0_16345071_9336.cpp:1:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algobase.h:261:5: note:   'std::max'
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^