#include <iostream>
#include <deque>

#define MAXN 5000002

using namespace std;

int A[MAXN], N, K;
long long S;
deque<int> q;

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();
        }

        if(!q.empty() && q.front() <= i - K) {
            q.pop_front();
        }

        q.push_back(i);
        if(i >= K) {
            S += A[q.front()];
        }

    }

    cout << S;

    return 0;
}