#include <bits/stdc++.h>
#define NMAX 5000005
#define ll long long 
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

int main()
{
    ll n, k, v[NMAX], ans=0;
    fin>>n>>k;

    for(ll i=1; i<=n; i++)
        fin>>v[i];

    deque<ll> Q;
    Q.push_back(1);

    for(ll i=2; i<=n; i++)
    {
        while(!Q.empty() && v[i] <= v[Q.back()])
            Q.pop_back();
        Q.push_back(i);

        if(i - Q.front() == k)
            Q.pop_front();
        
        if(i >= k)
            ans += v[Q.front()];
    }

    fout<<ans;

    return 0;
}