#include <iostream>
#include <fstream>
#include <set>
#include <vector>
#include <queue>
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

long long n, k;
long long sum;

set <long long> subsec;
queue <long long> copie;

void read(){
    fin>>n>>k;
    for(long long i=1; i<=k; i++){
        long long x;
        fin>>x;
        subsec.insert(x);
        copie.push(x);
    }
    sum+=*subsec.begin();
    //fout<<*subsec.begin()<<' ';
    for(long long i=k+1; i<=n; i++){
        long long x;
        fin>>x;
        subsec.erase(copie.front());
        copie.pop();
        copie.push(x);
        subsec.insert(x);
        //fout<<*subsec.begin()<<' ';
        sum+=*subsec.begin();
    }
    fout<<sum;
}

int main()
{
    read();
    return 0;
}