#include <cstdio>
#include<deque>
using namespace std;
const int N=5000001
int main()
{
    int i,n,k,v[N];
    long long suma=0;
    deque <int> my_deq;
    scanf("%d%d",&n,&k)
    for(i=0;i<n;i++)
    {
        scanf("%d",&v[i]);
        while (my_deq.size() && v[my_deq.back()]>=v[i])
            my_deq.pop_back();
        my_deq.push_back(i);
        if(my_deq.front()==i-k)
            my_deq.pop_front();
        if(i>=k-1)
            suma +=v[my_deq.front()];
    }
    g<<suma;
    return 0;
}