var n,i,s,k,min,j,pos:int64;
    f:text;
    v:array[1..5000000] of int64;
begin
assign(f,'deque.in');
reset(f);
read(f,n,k);
min:=maxlongint;
for i:=1 to k do begin
    read(f,v[i]);
    if min>v[i] then begin
       min:=v[i];
       pos:=i;
       end;
    end;
s:=min;
for i:=k+1 to n do begin
    read(f,v[i]);
    if v[i]<min then begin
       min:=v[i];
       pos:=i;
       end;
    if pos<=i-k then begin
       min:=maxlongint;
       for j:=i downto i-k+1 do
           if v[j]<min then begin
              min:=v[j];
              pos:=j;
              end;
       end;
    s:=s+min;
    end;
close(f);
assign(f,'deque.out');
rewrite(f);
write(f,s);
close(f);
end.