#include <fstream>
#include <cstdio>
#include <vector>
#include <deque>
#define NMAX 5000005
#define HMAX 100005
#define pb push_back
#define INF 0x3f3f3f3f

using namespace std;

typedef pair<int, int> pii;

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

int v[NMAX];

int main() {
	int n,k,i;
	long long sum=0;

	fin>>n>>k;
	for(i=1;i<=n;++i) fin>>v[i];

	deque<int> dq;
	for(i=1;i<=n;++i) {
		while(!dq.empty() && v[dq.back()]>v[i]) dq.pop_back();
		dq.push_back(i);

		if(dq.front()<=i-k)
			dq.pop_front();

		if(i>=k) sum+=1LL*v[dq.front()];
	}

	fout<<sum;

	return 0;
}