#include <fstream>
#define N 5000001
using namespace std;

FILE *fin=fopen("deque.in", "r"), *fout=fopen("deque.out", "w");

int a[N], b[N];

int main()
{
	int n, k, m1=1, m2=0, i;
	long long s=0;
	fscanf(fin, "%d%d", &n, &k);
	for(i=1;i<=n;i++)
	{
		fscanf(fin, "%d", &a[i]);
	}
	for(i=1;i<=n;i++)
	{
		while(m1<=m2&&a[i]<=a[b[m2]]) m2--;
		b[++m2]=i;
		if(b[m1]==i-k) m1++;
		if(i>=k) s+=a[b[m1]];
	}
	fprintf(fout, "%lld", s);
}