#include<cstdio>
#include<fstream>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<bitset>
#include<deque>
#include<queue>
#include<set>
#include<map>
#include<cmath>
#include<cstring>
#include<ctime>
#include<cstdlib>
#include<unordered_map>

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>

using namespace std;

const int nmax = 5000005;

int n, k, i, a[nmax];
ll s;

deque<int> q;

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);

    scanf("%d%d", &n, &k);

    for(i = 1; i <= n; i++)
    {
        scanf("%d", &a[i]);

        while(!q.empty() && a[i] <= a[q.back()])
            q.pop_back();

        q.pb(i);

        if(q.front() == i - k)
            q.pop_front();

        if(i >= k)
            s += a[q.front()];
    }

    printf("%lld\n", s);

    return 0;
}