#include <fstream>

using namespace std;

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

const int nmax=5000000;
int n,v[nmax+5],k;
int deq[nmax+5],st=1,dr=0;
long long ans=0;

int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
        while(st<=dr && v[i]<v[deq[dr]])
            dr--;
        if(st<=dr && deq[st]<=i-k)
            st++;
        deq[++dr]=i;
        if(i>=k)
            ans+=v[deq[st]];
    }
    fout<<ans;
    return 0;
}
/**
**/