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

int n, k, v[5000001], i, stanga=1, dreapta, aux[5000001];
long long s;

int main(){
    fin>>n>>k;
    for(i=1; i<=n; i++)
        fin>>v[i];

    for(i=1; i<=n; i++){
        while(stanga<=dreapta && v[i]<=v[aux[dreapta]])
            dreapta--;

        aux[++dreapta]=i;

        if(aux[stanga]==i-k)
            stanga++;

        if(k<=i)
            s+=v[aux[stanga]];
    }

    fout<<s;

    return 0;
}