#include <fstream>
using namespace std;
int n,i,V[5000010],P,j,d[5000010],k;
long long S;
int main (){
    ifstream fin ("deque.in");
    ofstream fout("deque.out");
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>V[i];
    d[1]=1;
    P=1;
    j=0;
    for(i=1;i<=n;i++)
    {
        while(P<=j&&V[i]<V[d[j]])
            j--;
        j++;
        d[j]=i;
        if(i-d[P]==k)
            P++;
        if(i>=k)
            S=S+V[d[P]];
    }
    fout<<S;
    return 0;
}