var v,d:array[1..5000000] of longint;
    i,n,k,p,u:longint;
    s:int64;
begin
assign(input,'deque.in');reset(input);
assign(output,'deque.out');rewrite(output);
readln(n,k);
for i:=1 to n do readln(v[i]);
p:=1;u:=0;s:=0;
for i:=1 to n do
begin
while (p<=u) and (v[i]<=v[d[u]]) do dec(u);
inc(u);
d[u]:=i;
if i-d[p]=k then inc(p);
if i>=k then inc(s,v[d[p]]);
end;
writeln(s);
end.