#include <bits/stdc++.h>
using namespace std;

#define NMAX 5000005

int v[NMAX];

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

	int n, k;
	scanf("%d%d", &n, &k);

	deque<int> dq;

	long long sum = 0;
	for (int i = 1; i <= n; ++i) {
		scanf("%d", &v[i]);
		while (!dq.empty() && v[dq.back()] >= v[i])
			dq.pop_back();
		while (!dq.empty() && i - dq.front() >= k)
			dq.pop_front();
		dq.push_back(i);
		sum += (i >= k) * v[dq.front()];
	}

	printf("%lld\n", sum);
}