#include<cstdio>
#include<deque>
using namespace std;
deque<int> d;
int v[5000003];
long long s;
int main()
{
    int n, k, i;
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d %d", &n, &k);
    for(i=1; i<=n; i++)
        scanf("%d", &v[i]);
    for(i=1; i<=n; i++)
    {
        while(!d.empty() && v[i]<=v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(i-k==d.front())
            d.pop_front();
        if(i>=k)
            s=s+v[d.front()];
    }
    printf("%lld", s);
    return 0;
}