#include<fstream>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<climits>
#include<iomanip>
#include<cstring>
#include<bitset>
using namespace std;

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

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

long long sum=0;
int d[5000005];
int v[5000005];
int n,k;
int st,dr,x;

int main(){

    f>>n>>k;

    for(int i=1;i<=n;i++){
        f>>v[i];
    }

    st=1;
    dr=1;
    d[1] = 1;

    for(int i=2;i<=n;i++){

        while(st<=dr && v[d[dr]]>=v[i]){
            dr--;
        }
        dr++;
        d[dr] = i;

        if(i-d[st]+1>k){
            st++;
        }

        if(i>=k){
            //cout<<v[d[st]]<<'\n';

            sum+=v[d[st]];
        }

    }

    g<<sum;

    f.close();
    g.close();
    return 0;
}