#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
typedef long long i64;
const int N = 1e6 + 10, INF = 0x3f3f3f3f;
int n, k;
int a[N];
struct Node {
int l, r;
i64 s, minv, mark;
}tr[N << 2];
void pushup(Node tr[], int u) {
tr[u].s = tr[u << 1].s + tr[u << 1 | 1].s;
tr[u].minv = min(tr[u << 1].minv, tr[u << 1 | 1].minv);
}
void build(Node tr[], int u, int l, int r) {
tr[u] = {l, r, a[r], a[r], 0};
if (l == r) return ;
int mid = l + r >> 1;
build(tr, u << 1, l, mid), build(tr, u << 1 | 1, mid + 1, r);
pushup(tr, u);
}
void push(Node tr[], int u, int k) {
tr[u].s += (tr[u].r - tr[u].l + 1) * k;
tr[u].minv += k;
tr[u].mark += k;
}
void pushdown(Node tr[], int u) {
if (tr[u].mark) {
push(tr, u << 1, tr[u].mark), push(tr, u << 1 | 1, tr[u].mark);
tr[u].mark = 0;
}
}
void update(Node tr[], int u, int l, int r, int k) {
if (tr[u].l >= l && tr[u].r <= r) {
push(tr, u, k);
return ;
}
int mid = tr[u].l + tr[u].r >> 1;
pushdown(tr, u);
if (l <= mid) update(tr, u << 1, l, r, k);
if (r > mid) update(tr, u << 1 | 1, l, r, k);
pushup(tr, u);
}
i64 query(Node tr[], int u, int l, int r, int type) {
if (tr[u].l >= l && tr[u].r <= r) return type ? tr[u].s : tr[u].minv;
int mid = tr[u].l + tr[u].r >> 1;
i64 res = type ? 0 : INF;
pushdown(tr, u);
if (l <= mid) res = query(tr, u << 1, l, r, type);
if (r > mid) {
i64 t = query(tr, u << 1 | 1, l, r, type);
res = type ? res + t : min(res, t);
}
return res;
}
int main() {
scanf("%d%d", &n, &k);
for (int i = 1; i <= n; i ++ ) scanf("%d", &a[i]);
build(tr, 1, 1, n);
i64 res = 0;
for (int i = 1; i + k - 1 <= n; i ++ ) {
i64 v = query(tr, 1, i, i + k - 1, 0);
if (v > 0) {
res += v;
update(tr, 1, i, i + k - 1, -v);
}
}
printf("%lld\n", res + query(tr, 1, 1, n, 1));
return 0;
}