#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque <int> d;
long long s = 0;
int a[5000001];
int main()
{
    int n,i,k;
    f>>n>>k;
    for(i=1;i<=n;i++)
    {
        f>>a[i];
        while(!d.empty()&&a[d.back()]>=a[i]) d.pop_back();
        d.push_back(i);
        if(i-d.front() >=k ) d.pop_front();
        if(i>=k) s+=a[d.front()];
    }
    g<<s;
    return 0;
}