#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,k,i,v[5000005];
long long s;
deque <long long> d;
int main()
{

    f>>n>>k;
    for(i=1;i<=n;++i)f>>v[i];
    d.push_back(1);
    for(i=1;i<=n;++i)
    {
        while(!d.empty() && v[i]<=v[d.back()])d.pop_back();
        d.push_back(i);
        if(i-d.front()>=k)d.pop_front();
        if(i>=k)s+=v[d.front()];
    }
    g<<s<<'\n';
    return 0;
}