requirement pivotal std::multimap

i have std::multimap where pivotal tradition class. something this:

class x {
public:
    std::string s;
    int x;
    user <(const x& other) const { relapse s < other.s; }
};
std::multimap<x, int> mymap;

now, i'd upper_bound lower_bound iterate over elements same value "s". i need exercise user x (for example: ==). work morally only this?

also, should i supply justification upper_bound lower_bound? i assume i should emanate pygmy vigilant preferred value "s"?