#include <cstdio>
#include <cstring>
#include <ctime>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>

using namespace std;
long long s;
int n, k, i, x, v[5000005];
deque <int> d, q;
int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);

    scanf("%d%d", &n, &k);
    scanf("%d", &x);

    d.push_back(1);q.push_back(x);

    for(i=2;i<=n;i++)
    {
        scanf("%d", &x);
        while(!q.empty()&&x<q.back()) q.pop_back(),d.pop_back();
        q.push_back(x);d.push_back(i);
        while(i-d.front()>=k) q.pop_front(),d.pop_front();
        if(i-k>=0) s+=q.front();
    }
    printf("%lld", s);
    return 0;
}