#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{int v[5000005], d[5000005], i, n, k, l, r;
long long int s;

    s = 0; l = 1; r = 0;

    f>>n>>k;

    for(i = 1; i <= n; i++)

        f>>v[i];


    for(i = 1; i <= n; i++){

        while(l <= r && v[i] <= v[d[r]])

            r--;

        r++;

        d[r] = i;

        if(d[l] <= i-k)
            l++;

        if(i >= k)
            s += v[d[l]];
    }
    g << s;

    return 0;
}