#include<fstream>

#define maxn 5000005

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

int n,k,front,back;
int v[maxn],deque[maxn];

int main () {
	
	f >> n >> k;
	for ( int i = 1 ; i <= n ; ++i ){
		f >> v[i];
	}
	
	long long sol = 0;
	front = 1; back = 0;
	for ( int i = 1 ; i <= n ; ++i ){
		
		while ( front <= back && v[deque[back]] >= v[i] ){
			--back;
		}
		deque[++back] = i;
		
		if ( i - deque[front] == k ){
			++front;
		}
		
		if ( i >= k ){
			sol += v[deque[front]];
		}
	}
	
	g << sol << "\n";
	
	f.close();
	g.close();
	
	return 0;
}