#include <fstream>
using namespace std;
#define dim 5000001
#define inf 0x3f3f3f
int stiva[dim];
int v[dim];

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