#include <bits/stdc++.h>
#define ll long long
#define all(a) (a).begin(), (a).end()
//#pragma GCC optimize("O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define sz() size()
#define fr first
#define sc second
#define pb push_back
#define er erase
#define in insert
#define pi pair<int,int>
#define pii pair<pair<int,int>,int>
#define mp make_pair
#define int long long
#define rc(s) return cout<<s,0
#define rcc(s) cout<<s,exit(0)
using namespace std;

const int mod=1e9+7;
const int modx=998244353;
const int per=666013;

const int inf=1e9;

int n,k,a[5000005],ans;
deque<int>dq;

int32_t main(){
	ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
    srand(chrono::steady_clock::now().time_since_epoch().count());
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin >> n >> k;
    for(int i=1;i<=n;i++) cin >> a[i];
    for(int i=1;i<=n;i++){
        while(dq.size()>=1 && a[dq.back()]>=a[i]) dq.pop_back();
        dq.push_back(i);
        if(i-dq.front()==k) dq.pop_front();
        if(i>=k) ans+=a[dq.front()];
    }
    cout << ans;
}