#include<fstream>
#include<set>
#define MAXN 5000001
#define LL long long
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
set<LL> T;
LL N,K,X[MAXN],rez;
int main() {
	LL i;
	cin>>N>>K;
	for(i=1;i<=N;i++)
	            cin>>X[i];	 		 
	for(i=1;i<=K;i++)
	         T.insert(X[i]);
	for(i=K+1;i<=N+1;i++) {
					rez+=*T.begin();
					T.erase(T.find(X[i-K]));
					T.insert(X[i]); }
cout<<rez;
return 0;
}