/in/foo.cc: In function 'int main()':
/in/foo.cc:31:38: error: no matching function for call to 'max(long long int)'
      f[i][j]=max(f[k][j-1]*nn[k][i-1]);
                                      ^
In file included from /usr/include/c++/6/bits/char_traits.h:39:0,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:2:
/usr/include/c++/6/bits/stl_algobase.h:219:5: note: candidate: template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^~~