#include <iostream>
#include <list>
using namespace std;
int main() {
list<pair<int, char>> pair_list;
pair_list.push_front(make_pair(1, 'a'));
pair_list.push_front(make_pair(2, 'b'));
pair_list.push_back(make_pair(10, 'x'));
pair_list.push_back(make_pair(20, 'y'));
for(auto itr=pair_list.begin();itr!=pair_list.end();itr++) {
cout << itr->first << ", " << itr->second << endl;
}
return 0;
}
// output
/*
2, b
1, a
10, x
20, y
*/