#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

deque <int> d;
long long s;
int a[5000001];
int main()
{
    int n,i,k;
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d%d", &n, &k);
    for(i=1;i<=n;i++)
    {
        scanf("%d", &a[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("%d", s);
    return 0;
}