#include <iostream>
#include <deque>

using namespace std;

#define maxN 5000005

deque <int> D;
int A[maxN];

int main()
{
	freopen ("deque.in", "r", stdin);
	freopen ("deque.out", "w", stdout);
	
	int N, K;
	long long S = 0;
	
	scanf ("%d %d", &N, &K);
	
	for (int i = 1; i <= N; ++ i)
	{
		scanf ("%d", &A[i]);
		
		if ( ! D.empty() )
			if (D.front() <= i - K) D.pop_front();
		
		while ( ! D.empty() && A[D.back()] > A[i] ) D.pop_back();
		
		D.push_back (i);
		
		if (i >= K) S += A[D.front()];
	}
	
	printf ("%lld", S);
	
	return 0;
}