#include <iostream>
#include <deque>
#include <fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque < int > Q;
#define MAX 5000005
int a[MAX];
int main()
{
    int n, k, s = 0;
    fin >> n >> k;
    for(int i = 1; i<=n; i++)
        fin >> a[i];

    for(int i = 1; i<=n; i++)
    {
        while(Q.size() && a[Q.front()]>a[i])
            Q.pop_front();
        Q.push_front(i);
        if(i - Q.back() == k)
            Q.pop_back();
        if(i >= k)
            s += a[Q.back()];
    }
    fout << s << "\n";
    return 0;
}