#include <bits/stdc++.h>
#define FILE_NAME "deque"
#define fast ios_base :: sync_with_stdio(0); cin.tie(0);
#pragma GCC optimize("O3")
#define NMAX 5000000
using namespace std;

ifstream f(FILE_NAME ".in");
ofstream g(FILE_NAME ".out");

typedef long long ll;
typedef long double ld;
typedef pair<int,int> pi;
typedef pair<ll,ll> llp;
typedef pair<ld,ld> pct;

const ll inf = 1LL << 60;
const ll mod = 1e9 + 7;
const ld eps = 1e-9;


void add(ll &a , ll b)
{
    a += b;
    a %= mod;
}

void sub(ll &a, ll b)
{
    a = (a - b + mod) % mod;
}

ll n, k, sum, v[NMAX];
deque <ll> Q;
int main()
{
    f >> n >> k;
    for(int i = 1; i <= n; ++i)
        f >> v[i];
    for(int i = 1; i <= n; ++i)
    {
        while(!Q.empty() && v[i] <= v[Q.back()]) Q.pop_back();
        Q.push_back(i);
        if(Q.front() == i - k) Q.pop_front();
        if(i - k >= 0)
            sum += v[Q.front()];
    }
    g << sum;

    f.close();
    g.close();
    return 0;
}