AtCoder Beginner Contest 075 D Axis-Parallel Rectangle

这么小的数据范围。暴力啊。不幸的是。暴力都写错了。。。写的O(n^{2)的，看了下别人的代码，大都是O(n}3)的，最无耻的是题解，竟然是O(n^5)
数据范围小也不能这样啊

#include <bits/stdc++.h>
using namespace std;
using LL = long long;

const int MAXN = 102;
LL x[MAXN],y[MAXN];
vector<LL> vx,vy;
int n,K;
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> K;
    for(int i = 0; i < n; ++i)
    {
        cin >> x[i] >> y[i];
        vx.push_back(x[i]);
        vy.push_back(y[i]);
    }
    sort(vx.begin(),vx.end());
    sort(vy.begin(),vy.end());
    LL res = 1LL<<62;
    for(int i = 0; i < vx.size(); ++i)
    {
        for(int j = i+1; j < vx.size(); ++j)
        {
            vector<LL> vz;
            for(int k = 0; k < n; ++k)
                if(x[k] >= vx[i] && x[k] <= vx[j])
                    vz.push_back(y[k]);
            sort(vz.begin(),vz.end());
            for(int k = 0; k <= (LL)vz.size()-K; ++k)
                res = min(res,(vx[j]-vx[i])*(vz[k+K-1]-vz[k]));
        }
    }
    cout << res <<endl;
    return 0;
}