#include < fstream >
using   namespace  std;

int  n,m;
int  a[ 101 ];
int  f[ 101 ][ 101 ];
int  cmp( const   void *  no1, const   void *  no2){
     return   * ( int   * )no1 -* ( int * )no2;
}
int  main()
{
    ifstream cin( " chop.in " );
    ofstream cout( " chop.out " );
    cin >> n >> m; m += 3 ;
     for ( int  i = 1 ;i <= n; ++ i) 
        cin >> a[i];
    qsort(a + 1 ,n, sizeof ( int ),cmp);
    memset(f, 0x7F , sizeof (f));
    f[ 0 ][ 0 ] = 0 ;
     for ( int  i = 1 ;i <= n; ++ i)
         for ( int  j = 1 ;j <= i / 2 ; ++ j){
            f[i][j] = f[i - 1 ][j];
             if (f[i][j] > f[i - 2 ][j - 1 ] + (a[i] - a[i - 1 ]) * (a[i] - a[i - 1 ]))
                f[i][j] = f[i - 2 ][j - 1 ] + (a[i] - a[i - 1 ]) * (a[i] - a[i - 1 ]);
        }
     if (f[n][m] < 0xFFFFFF )
        cout << f[n][m] << endl;
     else  
        cout <<- 1 << endl;
     return   0 ;
}