#include <bits/c++io.h>
#include <fstream>

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

#define nmax 5000010

int n, k, v[nmax], deque[nmax], start, finish;
long long sum;

int main()
{
    int i;
    fin >> n >> k;
    for (i = 1; i <= n; ++i)
        fin >> v[i];
    start = 1, finish = 0;
    for (i = 1; i <= n; ++i)
    {
        while (start <= finish && v[i] <= v[deque[finish]]) finish--;
        deque[++finish] = i;
        if (deque[start] == i-k) start++;
        if (i >= k) sum += v[deque[start]];
    }
    fout << sum;
    return 0;
}