#include <cstdio>
#include <deque>
#include <algorithm>
using namespace std;

int main() {
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    
    int N, K;
    scanf("%d %d", &N, &K);
    
    int* A = new int[N];
    for (int i = 0; i < N; ++i) {
        scanf("%d", &A[i]);
    }
    
    deque<int> dq;
    long long sum = 0;
    
    for (int i = 0; i < N; ++i) {
        while (!dq.empty() && A[dq.back()] >= A[i]) {
            dq.pop_back();
        }
        dq.push_back(i);
        
        while (!dq.empty() && dq.front() <= i - K) {
            dq.pop_front();
        }
        
        if (i >= K - 1) {
            sum += A[dq.front()];
        }
    }
    
    printf("%lld\n", sum);
    
    delete[] A;
    return 0;
}