#include <fstream>
using namespace std;

#define dim 5000001
int deque[dim];
int v[dim];


int main()
{
	ifstream fin("deque.in");
	ofstream fout("deque.out");
	int n, i, ls, ld, k;
	long long suma=0;
	
	fin>>n >>k;
	for(i=1;i<=n;++i)
		fin>>v[i];
	
	ls=1;
	ld=0;
	for(i=1;i<=n;++i)
	{
		while(ls<=ld && v[i]<=v[deque[ld]])--ld;
		deque[++ld]=i;
		
		if(i-deque[ls]>=k)
			++ls;
		
		if(i>=k)
			suma+=v[deque[ls]];
		
	}
	
	fout<<suma;
	return 0;
}