#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

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

deque <int> q;
int a[5000005];

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