#include <stdio.h>

using namespace std;
FILE *f=fopen("deque.in","r"), *g=fopen("deque.out","w");

int n, k, v[5000001], dq[5000001], p=1, u=0;
long long s=0;

int main()
{
	int i;
	
	fscanf(f, "%d%d", &n, &k);
	for(i=1;i<=n;++i)
		fscanf(f, "%d", &v[i]);

	for(i=1;i<=n;++i)
	{
		while(p<=u&&v[i]<=v[dq[u]])
			--u;
		dq[++u]=i;
		if(dq[p]<=i-k)
			++p;
		if(i>=k)
			s+=v[dq[p]];
	}
	
	fprintf(g, "%lld", s);
	
	return 0;
}