#include <stdio.h>
#include <deque>

using namespace std;

FILE *fin = fopen("deque.in", "r");
FILE *fout = fopen("deque.out", "w");

#define MAXN 5000001

deque <int> q;

int N, K;
int v[MAXN];long long sum;

int main()  {
    fscanf(fin, "%d%d", &N, &K);
    for(int i = 1;i <= N;i++)  {
        fscanf(fin, "%d", &v[i]);
    }
    for(int i = 1;i <= N;i++)  {
        while(!q.empty() && v[i] <= v[q.back()])
            q.pop_back();
        q.push_back(i);
        if(q.front() == i - K)
            q.pop_front();
        if(i >= K)
            sum += 1LL * v[q.front()];
    }
    fprintf(fout, "%lld", sum);
    fclose(fin);
    fclose(fout);
    return 0;
}