#include <fstream>
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

long long n, k, i, p, u, s;
long long v[5000002], d[5000002];

int main(){
	fin >> n >> k;
	p = 1;
	u = 1;
	d[p] = 1;
	for(i = 1; i <= n; i ++)
		fin >> v[i];
	for(i = 2; i <= n; i ++){
		while(p <= u && v[i] < v[d[u]])
			u --;
		u ++;
		d[u] = i;
		if(i - d[p] == k)
			p ++;
		if(i >= k)
			s += v[d[p]];
	}
	fout << s;
	return 0;
}