#include <fstream>

using namespace std;

#define maxN 5000005

int A[maxN], D[maxN];

int main()
{
	ifstream f("deque.in");
	ofstream g("deque.out");
	
	int N, K;
	long long S = 0;
	
	f >> N >> K;
	
	int st = 1, dr = 0;
	
	for (int i = 1; i <= N; ++ i)
	{
		f >> A[i];
		
		if (st <= dr && D[st] <= i - K) ++ st;
		
		while (st <= dr && A[D[dr]] > A[i]) -- dr;
		
		D[++ dr] = i;
		
		if (i >= K) S += A[D[st]];
	}
	
	g << S;
	
	return 0;
}