#include <cstdio>
#include <deque>

using namespace std;

deque <int> dq;
int v[5000005];

int main() {
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);

    int n, k;
    long long rasp = 0;
    scanf("%d%d", &n, &k);

    for(int i = 1; i <= n; ++ i) {
        scanf("%d", &v[i]);
        while(!dq.empty() && v[i] <= v[dq.back()]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if(i - dq.front() + 1 > k) {
            dq.pop_front();
        }
        if(i >= k) {
            rasp += v[dq.front()];
        }
    }

    printf("%lld", rasp);

    return 0;
}