#include <iostream>
#include <deque>
#include <fstream>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> d;
int v[5000000];

int main()
{
    int i,s=0,n,k;
    fin>>n>>k;
    for(i=1;i<=n;++i) fin>>v[i];
    for(i=1;i<=n;++i)
     {
        while(!d.empty() && v[d.back()]>=v[i])
            d.pop_back();
        d.push_back(i);
        if(i-k==d.front())
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];
}
    fout<<s;
    return 0;
}