How to sort a vector containing objects of class in C++?

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  struct staff
  {
    int id;
    string name;
    string cls;
  };

  vector <staff> s = {
  {234, "Mark", "Biology"},
  {3455, "Mitch", "English"},
  {1234, "Hen", "Maths"}
  };

  sort( s.begin(), s.end(), [](const staff &a, const staff &b){ return (a.id < b.id);});

  for (const auto  & x : s)
    cout << x.id << ", " << x.name << ", " << x.cls << endl;
}