#include<bits/stdc++.h>
#define in f
#define out g
using namespace std;

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


int n;
int k;
int s;
int v[100010];
set<int>setu;

int main() {

    in >> n;
    in >> k;

    for(int i = 0; i < n; i++) {
        in >> v[i];
        setu.insert(v[i]);
        if(setu.size() == k) {
            s = s + *setu.begin();
            setu.erase(v[i - k + 1]);
        }
    }
    out << s;

}