#include <bits/stdc++.h>

using namespace std;
int a[5000030];

int main(){    
    deque<int> de;
    int n, k;
    long long s = 0;
    ifstream f("deque.in");
    ofstream g("deque.out");
    f>>n>>k;
    for (int i=1; i<=n; i++)
        f>>a[i];
    for (int i=1; i<=n; i++){
        while (!de.empty() && a[i] < de.back())
            de.pop_back();
        de.push_back(a[i]);
        if (i>=k && de.front() == a[i-k])
            de.pop_front();
        if (i>=k)
            s += de.front();
    }
       
    g<<s;
    return 0;
}