#include <bits/stdc++.h>
#define nMax 10000001
using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

int main(){
    int n,k;f>>n>>k;
    int x,minn=nMax,minn2=nMax,s=0,pm1=1,pm2;int ok=0;
    vector <int> v;
    for(int i=0;i<n;++i) {f>>x;v.push_back(x);}
    for(int i=0;i<n;++i){
            if(v[i]<=minn) {minn=v[i];pm1=i;minn2=nMax;}
            else if(v[i]<=minn2) {minn2=v[i];pm2=i;}
            if(i>=k&&i-ok>=k) s+=minn;
            //g<<"minn="<<minn<<"   minn2="<<minn2<<'\n';
            if(i-pm1+1>=k){
                minn=minn2;pm1=pm2;minn2=nMax;ok=i;i=pm2;
            }



    }
    g<<s;
}