#include <fstream>
#include <set>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");

multiset<int> myset;
multiset<int>::iterator it;
int a[5000005];
int n,k,i;
int main()
{
    fin>>n>>k;

    for(i=1;i<=k;++i) fin>>a[i], myset.insert(a[i]);

    long long sol=0;

    sol+=(long long)*myset.begin();

    for(i=k+1;i<=n;++i)
    {
        fin>>a[i];
        myset.insert(a[i]);
        myset.erase(myset.find(a[i-k]));
        sol+=(long long)*myset.begin();

    }

    fout<<sol;
    return 0;
}