dictionary - C++ map comparator -

for c++ map declared like:

map < set<int>,int > x; 

what default comparator function compiler uses?
code using statement executed not sure comparator uses.

for std::map<k, t>, default comparator std::less<k>.

std::less<k> uses lhs < rhs default way compare.

in case, end using:

bool operator<(std::set<int> const& lhs, std::set<int> const& rhs)