#include<bits/stdc++.h>
using namespace std;
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define dbg(x) cout << #x << '=' << x << '\n';
#define ll long long
#define sz size()
#define x first
#define y second
#define pi pair <int, int>
#define pii pair <int, pi>
#define vi vector <int>
const ll mod = 998244353;
int n, k, a[5000001];
deque <int> q;
ll s;

int32_t main(){
    ios_base :: sync_with_stdio(0); cin.tie(); cout.tie();
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin>>n>>k;
    for(int i=1; i<=n; i++){
        int x;
        cin>>x;
        a[i]=x;
        while(!q.empty() &&  x<=a[q.back()]) q.pop_back();
        q.push_back(i);
        if(q.front()==i-k) q.pop_front();
        if(i>=k) s+=1LL*a[q.front()];
    }
    cout<<s;
}