#include <stdio.h>
#include <deque>
#define MAXN 5000005
using namespace std;

int n, k, v[MAXN];
deque<int> dq;

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", &v[i]);

    long long sol = 0;
    for(int i = 1; i < k; i++) {
        while(!dq.empty() && v[dq.back()] >= v[i]) dq.pop_back();
        dq.push_back(i);
    }
    for(int i = k; i <= n; i++) {
        while(!dq.empty() && i - dq.front() + 1 > k) dq.pop_front();
        while(!dq.empty() && v[dq.back()] >= v[i]) dq.pop_back();
        dq.push_back(i);

        sol += v[dq.front()];
    }

    printf("%lld\n", sol);

    return 0;
}