#include <stdio.h>
#include <deque>
#define maxn 5000010

using namespace std;

int N, K;
int A[maxn];//, Deque[maxn];
deque <int> q;
int Front, Back;
long long Sum;

int main() {
    freopen ("deque.in", "r", stdin);
    freopen ("deque.out", "w", stdout);
    scanf ("%d %d", &N, &K);
    for (int i = 1; i <= N; ++i)
        scanf ("%d", &A[i]);

    for (int i = 1; i <= N; ++i) {
        while (!q.empty() && A[q.back()]>=A[i] )
            q.pop_back();
        q.push_back(i);
        if (q.front() == i-K)
            q.pop_front();
        if (i >= K)
            Sum += A[q.front()];
    }
    printf("%lld\n", Sum);
    return 0;
}