#include <iostream>
#include <cstdio>
#include <deque>
#define NMAX 5000001

using namespace std;

int n, k, a[NMAX];
long long s;
deque <int> d;

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(!d.empty() && a[d.back()] >= a[i])
            d.pop_back();

        d.push_back(i);

        if(i - d.front() == k) d.pop_front();
        if(i >= k) s += a[d.front()];
    }

    printf("%lld", s);

    return 0;
}