multimap查询重复键值

typedef std::multimap<int, int> Pairs;
Pairs pairs;
pairs.insert(make_pair(1, 1));
pairs.insert(make_pair(1,2));
pairs.insert(make_pair(1,3));
pairs.insert(make_pair(2, 4));
pairs.insert(make_pair(2,5));
pairs.insert(make_pair(3,2));
int key = 1;
Pairs::iterator position = pairs.lower_bound(key);
while (position != pairs.upper_bound(key))
{
    cout << position->first << "\t" << position.second;
    ++position;
}