#include <iostream>
#include <fstream>
#include <set>
#define int long long
using namespace std;
const int dim=5e6+5;
int a[dim],n,k,suma;
multiset<int> s;
signed main(){
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin>>n>>k;
    for(int i=1;i<=k;i++){
        cin>>a[i];
        s.insert(a[i]);
    }
    multiset<int>::iterator it=s.begin();
    suma+=(*it);
    int p=1;
    for(int i=k+1;i<=n;i++){
        s.erase(s.find(a[p]));
        p++;
        cin>>a[i];
        s.insert(a[i]);
        it=s.begin();
        suma+=(*it);
    }
    cout<<suma;
    return 0;
}