#include<fstream>
#include<algorithm>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int v[5000005],poz[5000005],x[5000005];
long long n,m,i,j,k,maxim,s,sum,p,u;
int main(){
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>v[i];
    p=1;
    u=1;
    x[1]=v[1];
    poz[1]=1;
    for(i=2;i<=n;i++){
        if(i-poz[p]+1>k)
            p++;
        u++;
        x[u]=v[i];
        poz[u]=i;
        while(x[u]<=x[u-1]&&u>p){
            x[u-1]=x[u];
            poz[u-1]=poz[u];
            u--;
        }
        if(i>=k)
            sum+=x[p];

    }
    fout<<sum;
    return 0;
}