2.2.7.1 Sets - iterators

#include <iostream>
#include <set>

using namespace std;

int main()
{
    set<int> s1;
    set<int> s2;
    unsigned start_value;
    cin >> start_value;
    unsigned stop_value;
    cin >> stop_value;

    for(int i =start_value; i <= stop_value; i++){
        if(i%2==0) {
            s1.insert(i);
        }else {
            s2.insert(i);
        }
    }
    for(auto i = s1.begin();i!=s1.end();i++){
        for(auto j = s2.begin(); j!=s2.end(); j++){
            cout << *i + *j << " ";
        }
        cout << endl;
    }
    for(auto i = s1.rbegin();i!=s1.rend();i++){
        for(auto j = s2.rbegin(); j!=s2.rend(); j++) {
            cout << *i + *j << " ";
        }
    }
    for(auto i = s1.rbegin();i!=s1.rend();i++){
        for(auto j = s2.rbegin(); j!=s2.rend(); j++){
            cout << *i + *j << " ";
        }
    }
    
    cout << endl;
    return 0;
}