#include <iostream>
#include<deque>
#include<fstream>
using namespace std;
int i,k,n;
long long s,x,v[5000001];
deque<int> d;
int main()
{
    ifstream f("deque.in");
    f>>n>>k>>v[1];
    d.push_front(1);
    for(i=1;i<n;++i)
    {
        if(d.back()<i-k+2)d.pop_back();
        f>>v[i+1];
        if(v[d.back()]>v[i+1])
        {
            d.push_back(i+1);
            while(v[d.front()]!=v[i+1])
                d.pop_front();
        }
        else
        {
            while(v[d.front()]>v[i+1])
                d.pop_front();
            d.push_front(i+1);
        }
        if(i+2>k)s+=v[d.back()];
    }
    ofstream g("deque.out");
    g<<s;
    return 0;
}