#include <stdio.h>
#include <stdlib.h>

using namespace std;

#define maxn 5000010

long long Sum;
int N, K, L;
int A[maxn];
int H[maxn], P[maxn];

void push(int x)
{
	int aux;

	while (x/2>=1 && A[H[x]] < A[H[x/2]])
	{
		aux = H[x], H[x] = H[x/2], H[x/2] = aux;

		P[H[x]] = x;
		P[H[x/2]] = x/2;
		x /= 2;
	}
}

void pop(int x)
{
	int aux, y = 0;

	while (x != y)
	{
		y = x;
		if (y*2<=L && A[H[x]]>A[H[y*2]]) x = y*2;
		if (y*2+1<=L && A[H[x]]>A[H[y*2+1]]) x = y*2+1;

		aux = H[x], H[x] = H[y], H[y] = aux;
		P[H[x]] = x;
		P[H[y]] = y;
	}
}

int main()
{
	freopen("deque.in", "r", stdin);
	freopen("deque.out", "w", stdout);

	scanf("%d %d ", &N, &K);

	int i;

	for (i = 1; i <= N; i++)
	{
		scanf("%d ", &A[i]);

		L++;
		H[L] = i;
		P[H[L]] = L;
		push(L);

		while (H[1] <= i-K)
		{
			H[1] = H[L--];
			P[H[1]] = 1;
			pop(1);
		}

		if (i >= K)	Sum += A[H[1]];
	}

	printf("%lld\n", Sum);

	return 0;
}