#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define pii              pair <int,int>
#define pll              pair <long long,long long>
#define sc               scanf
#define pf               printf
#define Pi               2*acos(0.0)
#define ms(a,b)          memset(a, b, sizeof(a))
#define pb(a)            push_back(a)
#define MP               make_pair
#define db               double
#define ll               long long
#define EPS              10E-10
#define ff               first
#define ss               second
#define sqr(x)           (x)*(x)
#define D(x)             cerr<<#x " = "<<(x)<<endl
#define VI               vector <int>
#define DBG              pf("Hi\n")
#define MOD              1000000007
#define CIN              ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define SZ(a)            (int)a.size()
#define sf(a)            scanf("%d",&a)
#define sfl(a)           scanf("%lld",&a)
#define sff(a,b)         scanf("%d %d",&a,&b)
#define sffl(a,b)        scanf("%lld %lld",&a,&b)
#define sfff(a,b,c)      scanf("%d %d %d",&a,&b,&c)
#define sfffl(a,b,c)     scanf("%lld %lld %lld",&a,&b,&c)
#define stlloop(v)       for(__typeof(v.begin()) it=v.begin();it!=v.end();it++)
#define loop(i,n)        for(int i=0;i<n;i++)
#define loop1(i,n)       for(int i=1;i<=n;i++)
#define REP(i,a,b)       for(int i=a;i<b;i++)
#define RREP(i,a,b)      for(int i=a;i>=b;i--)
#define TEST_CASE(t)     for(int z=1;z<=t;z++)
#define PRINT_CASE       printf("Case %d: ",z)
#define LINE_PRINT_CASE  printf("Case %d:\n",z)
#define CASE_PRINT       cout<<"Case "<<z<<": "
#define all(a)           a.begin(),a.end()
#define intlim           2147483648
#define infinity         (1<<28)
#define ull              unsigned long long
#define gcd(a, b)        __gcd(a, b)
#define lcm(a, b)        ((a)*((b)/gcd(a,b)))

using namespace std;

//using namespace __gnu_pbds;
//typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;


/*----------------------Graph Moves----------------*/
//const int fx[]={+1,-1,+0,+0};
//const int fy[]={+0,+0,+1,-1};
//const int fx[]={+0,+0,+1,-1,-1,+1,-1,+1};   // Kings Move
//const int fy[]={-1,+1,+0,+0,+1,+1,-1,-1};  // Kings Move
//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move
//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move
/*------------------------------------------------*/

/*-----------------------Bitmask------------------*/
//int Set(int N,int pos){return N=N | (1<<pos);}
//int reset(int N,int pos){return N= N & ~(1<<pos);}
//bool check(int N,int pos){return (bool)(N & (1<<pos));}
/*------------------------------------------------*/

vector<pii>v;
vector<int>x,y;

map<int,int>mpx,mpy,imapx,imapy;

int dp[60][60],ara[60][60];

int main()
{
//    freopen("in.txt","r",stdin);
//	  freopen("out.txt","w",stdout);

    int n,kk;
    sff(n,kk);
    loop(i,n)
    {
        int a,b;
        sff(a,b);
        v.pb(pii(a,b));
        x.pb(a);
        y.pb(b);
    }

    sort(all(x));
    sort(all(y));

    int numx=0;
    for(int i:x)
    {
        if(mpx[i]==0)
        {
            mpx[i]=++numx;
            imapx[numx]=i;
        }
    }
    int numy=0;
    for(int i:y)
    {
        if(mpy[i]==0)
        {
            mpy[i]=++numy;
            imapy[numy]=i;
        }
    }

    for(pii x:v)
    {
        int a=mpx[x.ff];
        int b=mpy[x.ss];
        dp[a][b]++;
    }

//    for(int i=0; i<=numx; i++,cout<<endl)
//        for(int j=0; j<=numy; j++)
//            cout<<dp[i][j]<<" ";
//
//
//    D("-----------------");

    for(int i=1; i<=numx; i++)
        for(int j=1; j<=numy; j++)
            dp[i][j]+=dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1];

//    for(int i=0; i<=numx; i++,cout<<endl)
//        for(int j=0; j<=numy; j++)
//            cout<<dp[i][j]<<" ";
//    D("-------------------");
//    cout<<endl;

    ull ans=1LL<<63;
//    sort(all(v));

    for(int i=1;i<=numx;i++)
    {
        for(int j=1;j<=numy;j++)
        {
            for(int k=1;k<=i;k++)
            {
                for(int l=1;l<=j;l++)
                {
                    int a=dp[i][j]-dp[k-1][j]-dp[i][l-1]+dp[k-1][l-1];
                    if(a>=kk)
                    {
                        ull aa=imapx[i]-imapx[k];
                        ull bb=imapy[j]-imapy[l];
                        ans=min(ans,aa*bb);
                    }
                }
            }
        }
    }


    printf("%llu\n",ans);

    return 0;
}


Measured memory_bytes: 256