#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <iostream>
#include <set>
#include <deque>
#include <fstream>

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

#define NMAX 500010

deque<pair<int, int>> Q;
int n, x, k;
long long s;

int main()
{
    fin>>n>>k;
    for(int i = 1; i <= n; i++)
    {
        fin>>x;
        while(Q.size() && Q.back().second > x)
            Q.pop_back();
        Q.push_back(make_pair(i, x));
        if(Q.front().first == i - k)
            Q.pop_front();
        if(i >= k)
            s += Q.front().second;
    }
    fout<<s;
    return 0;
}