COWS

program zad_k;

{$APPTYPE CONSOLE}

uses
    SysUtils;

const
    MAXN = 11000;

var
    a: array [0..MAXN] of integer;
    k, r, l, b, c, j, n, i, m: integer;

function f(m: integer): integer;
var
    i, b, c: integer;
begin
    b := 1;
    c := 1;
    for i := 2 to n do
        if (a[i] - a[c] >= m) then begin
            c := i;
            inc(b);
        end;
    f := b;
end;

begin
    readln(n, k);
    for i := 1 to n do
        read(a[i]);
    readln;

    if (k = 2) or (n = 3) then begin
        writeln(a[n] - a[1]);
        exit;
    end;
    r := a[n] - a[1];
    l := 0;
    while (r <> l) do begin
        m := (l + r) div 2;
        if (f(m) >= k) then
            l := m + 1
        else
            r := m;
    end;
    writeln(l - 1);
    readln;
end.