#include <fstream>
#include <deque>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

int main()
{
    deque <pair<int,int>> d;
    int n,k,x;
    fin>>n>>k;
    long long int sumMin=0;

    for(int i=0;i<n;i++)
    {
        fin>>x;

        if(!d.empty() && i-d.front().second>=k)
            d.pop_front();
        while(!d.empty() && x<d.back().first)
            d.pop_back();
        d.push_back({x,i});

        if(i>=k-1)
            sumMin+=d.front().first;
    }

    fout<<sumMin;

    return 0;
}