#include<fstream>
#include<deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
deque <pair<int,int>> dq;
#define fs first
#define sc second
int n,k,s,x,i;
int main(){
    cin>>n>>k>>x;
    dq.push_back({x,++i});
    while(n--){
        cin>>x;
        while(!dq.empty() && x<=dq.back().fs)
            dq.pop_back();
        dq.push_back({x,++i});
        if(dq.front().sc==i-k)
            dq.pop_front();
        if(i>=k)
            s+=dq.front().fs;
    }
    cout<<s;
}