#include <bits/stdc++.h>
#define int long long
using namespace std;

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

const int dim=5000009;

int n,k,v[dim];

multiset<int>s;

signed main(){
        fin>>n>>k;
    for(int i=1;i<=n;i++){
        fin>>v[i];
    }
    for(int i=1;i<k;i++){
        s.insert(v[i]);
    }
    int ans=0;
    for(int i=k;i<=n;i++){
        s.insert(v[i]);
        ans+=*s.begin();
        s.erase(v[i-k+1]);
    }
        fout<<ans;
}