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

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

deque<int> dq;
long long n, k, s;
int a[5000005];

int main() {
    fin>>n>>k;
    for(int i = 1;i <=n; ++i)
    {
        fin>>a[i];
    }
    for(int i = 1; i <= n; ++i)
    {
        while(!dq.empty() && a[dq.back()]>=a[i])dq.pop_back();
        dq.push_back(i);
        while(dq.front()<=i-k)dq.pop_front();
        if(i>=k){
        s+=a[dq.front()];
        }
    }
    fout<<s;
    return 0;
}