//#define debug //*******************************************************************************************************************************************
#ifdef debug
#include <chrono>
#endif

#include <iostream>
#include <algorithm> // next_permutation
#include <iomanip>
#include <cmath>
#include <vector>
#include <sstream>
#include <string>
#include <cstring> //memcpy
#include <cstdio>
#include <stack>
#include <queue>
#include <list>
#include <numeric> //accumulate
//#include <map>
//#include <unordered_map> //hash func.
#include <fstream> //ifstream, ofstream

//#define NDEBUG //If NDEBUG is defined before #include <cassert>, assert will be ignored. You had better define NDEBUG when u submit the code.
#include <cassert> //assert

using namespace std;


#define dout cout
//If u wanna output to a text file instead of standard output, plz define OUTPUTFILE.
//#define OUTPUTFILE "output.txt" //*******************************************************************************************************************************************
#ifdef OUTPUTFILE
#define dout outputfile
ofstream outputfile(OUTPUTFILE);
#define OutputFilePath "/Users/Nag/Documents/Prgm/Test/DerivedData/Test/Build/Products/Debug/output.txt"
#endif


#define din cin
//If u wanna input from a text file instead of standard input, plz define INPUTFROMTEXTFILEを.
//#define INPUTFILE "input.txt" //*******************************************************************************************************************************************
#ifdef INPUTFILE
#define din inputfile
ifstream inputfile(INPUTFILE);
#endif

#define scan(A) scanf("%d", &(A))
#define disp(A) dout << #A << " = " << setw(3) << (A) << endl
#define disP(A) dout << setw(3) << (A) << " "
#define rep(i,a,n) for(int (i)=(a); (i)<(n); (i)++)
#define dispAll(A,n) dout << #A << " = "; rep(j, 0, (n)) {disP(A[j]);} dout << endl
//#define dispAll(A,n) cout << #A << " = "; rep(j, 0, (n)) {cout << setw(3) << A[j] << " ";} cout << endl

#define sign(x) ((x)>0)-((x)<0) //x<0: -1, x=0: 0, x>0: +1
#define p(i) (i)/2
#define l(i) (i)*2
#define r(i) (i)*2+1

typedef pair<int,int> pii;
typedef vector<int> vi;
typedef unsigned long long ll;

const int INF = 2e9+10;
const ll INF_LL = 1e19; //Be careful for overflow.
const int NONE = -1;
const ll MOD = 1e9+7;

const int N_MAX = 51; //num of vertex or element
const int M_MAX = 100000; //num of edge
const int DATA_MAX = 1000000010;


int N;
int K;
int V[N_MAX][2]; //set of vertex.  id, x-axis, y- axis
#define id 0
#define x 0
#define y 1

void display() {
    
    dout << "----\n";
    rep(i,0,N) {
        disP(i); dout << " = " << V[i][id] << " : " << V[i][x] << ", " << V[i][y] << endl;
    }
    dout << "----\n";
    dout << "----\n";
}



int main() {
    //------------------------------------------------------------------------------------------
#ifdef debug
    //start timer
    auto startTime = chrono::system_clock::now();
#endif
    //------------------------------------------------------------------------------------------
    
    //cin, coutの高速化  ＊注意：cinを使うなら全部cinで、scanfを使うなら全部scanfで統一するように！
    cin.tie(0); //cinとcoutの同期を切る
    ios::sync_with_stdio(false); //iostreamとstdioの同期を切る
    
    //read input data
    din >> N >> K;
    int xx, yy;
    rep(i,0,N) {
        din >> xx >> yy;
        V[i][x] = xx;
        V[i][y] = yy;
    }
    
#ifdef debug
    display();
#endif
    
    //calc.
    int x_left, x_right, y_bot, y_top;
    int numOfVertexInRectangle;
    ll minArea = INF_LL;
    
    rep(x1,0,N) {
        x_left = V[x1][x];
        
        rep(x2,0,N) {
            if(x_left>=V[x2][x]) continue;
            x_right = V[x2][x];
            
            rep(y1,0,N) {
                y_bot = V[y1][y];
                
                rep(y2,0,N) {
                    if(y_bot>=V[y2][y]) continue;
                    y_top = V[y2][y];
                    
                    numOfVertexInRectangle = 0;
                    rep(i,0,N) {
                        if(x_left <= V[i][x] && V[i][x] <= x_right && y_bot <= V[i][y] && V[i][y] <= y_top ) {
                            numOfVertexInRectangle++;
#ifdef debug
                            dout << "--\n";
                            disp(V[i][x]);
                            disp(V[i][y]);
#endif
                        }
                    }
                    
                    if(numOfVertexInRectangle>=K) {
                        ll area = 1LL * (x_right - x_left)*(y_top - y_bot);
                        if( area < minArea ) minArea = area;
                    }
#ifdef debug
                    dout << "--------------\n";
                    disp(x_left);
                    disp(x_right);
                    disp(y_bot);
                    disp(y_top);
                    disp(numOfVertexInRectangle);
                    disp(K);
                    disp(minArea);
#endif
                }
            }
        }
    }
    
    
    dout << minArea << endl;
    
    
    
    //------------------------------------------------------------------------------------------
#ifdef debug
    //stop timer
    auto endTime = chrono::system_clock::now();
    auto dur = endTime - startTime;
    auto msec = chrono::duration_cast<chrono::milliseconds>(dur).count();
    dout << fixed << setprecision(4) << (double)msec/1000 << " sec \n";
#endif
    //------------------------------------------------------------------------------------------
    
#ifdef INPUTFILE
    inputfile.close();
#endif
    
#ifdef OUTPUTFILE
    outputfile.close();
    cout << "\"" << OutputFilePath << "\"" << endl;
#endif
    
    return 0;
}


Measured memory_bytes: 256