#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(a) (a).begin(), (a).end()
#define forn(i,a,b) for (int i = a; i <= b; i++)
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define rc(s) return cout<<s,0
#define pi pair <int, int>
#define sz(x) (int)((x).size())
#define make_unique(v) v.erase(unique(all(v)),v.end())
#define int long long

const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

const ll inf = 0x3f3f3f3f3f3f3f;
const ll mod = 1e9 + 7;
const int N = 5e6 + 11;

int n,k,a[N],deq[N],m;



int32_t main(){
ios_base::sync_with_stdio(0); cin.tie(0); cerr.tie(0); cout.tie(0);

ifstream cin("deque.in");
ofstream cout("deque.out");
    cin >> n >> k;

    for(int i = 1; i <= n; i++){
        cin >> a[i];
    }

    int Front = 1;
    int Back = 1;

    deq[1] = 1;

    int ans = 0;
    for(int i = 2; i <= n; i++){

        while(a[deq[Back]] >= a[i] && Front <= Back)Back--;
        deq[++Back] = i;

        if(deq[Front] <= i-k)Front++;

        if(i >= k)ans += a[deq[Front]];
    }

    cout << ans;

 //   rc(t[1]);
return 0;
}