#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,i,a[5000002];
long long s;
deque <int> d;
int main()
{
    fin>>n>>k;
    for(i=1;i<=n;++i)
    {
        fin>>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()];
    }
    fout<<s;
    return 0;
}