#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

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

deque <pair<int, int>> D;

int main()
{
    int N, K, a;
    f >> N >> K;
    long long sMin = 0;
    for(int i = 1; i <= N; i++)
    {
        f >> a;
        while(!D.empty() && a <= D.back().first)
            D.pop_back();
        D.push_back({a, i});
        if(i >= K)
        {
            if(D.front().second == i - K)
                D.pop_front();
            sMin += D.front().first;
        }
    }
    g << sMin;
    f.close();
    g.close();
    return 0;
}