program z2;

{$APPTYPE CONSOLE}

var f1,f2:text;
    a,b,n,i,j,m,k,l:integer;
    max,sum,min,m_n,sum1:int64;
    ma:array [1..100000] of word;
    r:array [1..100000] of int64;
    flag:boolean;
begin
assign(f1,'holy.in');
assign(f2,'holy.out');
reset(f1);
readln(f1,n,m);
for i:=1 to n do
begin
read(f1,a);
ma[a]:=ma[a]+1;
if max<a then max:=a;
end;
k:=0;
close(f1);
for i:=max downto 2 do
 begin
  if ma[i]>0 then
   begin
   if ma[i]=1 then
   begin
    j:=i-1;
    while (ma[j]=0) and (j>0) do j:=j-1;
    if j<>0 then
    begin
    k:=k+1;
    r[k]:=i-j;
    end;
   end else
   begin
    for l:=1 to  ma[i]-1 do
     begin
     k:=k+1;
     r[k]:=0;
     end;
    j:=i-1;
    while (ma[j]=0) and (j>0) do j:=j-1;
    if j<>0 then
    begin
    k:=k+1;
    r[k]:=i-j;
    end;
   end;
   end;
 end;
l:=1;
min:=r[1];
flag:=true;
m_n:=1;
while (flag<>false) and (l<k+1) do
begin
//flag:=false;
l:=l+1;
if min>r[l] then
 begin
 min:=r[l];
 m_n:=l;
 end;
if min=0 then flag:=false;
end;
rewrite(f2);
if m_n-m+1<1 then
 begin
 for i:=1 to m-1 do sum:=sum+r[i+m_n-1];
 writeln(f2,sum);
 end else
 begin
 for i:=1 to m-1 do sum:=sum+r[i+m_n-1];
 for i:=1 to m-1 do sum1:=sum1+r[i-m_n+1];
 if sum<sum1 then writeln(f2,sum) else writeln(f2,sum1);
 end;



close(f2);
end.