When my sort compare function is:
bool cmp(pair<int, int> p1, pair<int, int> p2)
{
    if(p1.first != p2.first)
        return p1.first < p2.first;
    else
        return p1.second >= p2.second;
}

I get WA#14.
And then delete the "=" like :
bool cmp(pair<int, int> p1, pair<int, int> p2)
{
    if(p1.first != p2.first)
        return p1.first < p2.first;
    else
        return p1.second > p2.second;
}
I get AC;