#include <iostream>
#include <fstream>
#include <deque>
#define pii pair<int, int>
using namespace std;

pii q[5000005];
long long ret;

int main()
{
    ifstream f("deque.in");
    ofstream g("deque.out");
    int n, k, x, l = 1;
    f >> n >> k;
    for(int i = 1; i <= n; i ++) {
        f >> x;
        while(q[0].first >= l && q[q[0].first].first > x)
            q[0].first --;
        q[++ q[0].first] = {x, i};
        if(i >= k) {
            while(q[0].first >= l && q[l].second <= i - k) l ++;
            ret += q[l].first;
        }
    }
    g << ret << "\n";
    return 0;
}