#include <bits/stdc++.h>

using namespace std;

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

long long k,n,v[5000001],st = 0,dr = -1,d[5000001],s;

int main()
{
     in>>n>>k;
    for (int i = 1;i <= n;++i)
        {in>>v[i];
        //se scoate din stanga daca e cazul
        if (st <= dr && d[st] == i - k)
            ++st;
        //se scoate din dreapta
        while (st <= dr && v[i] <= v[d[dr]])
               --dr;
        d[++dr] = i;
        if (i >= k)
            s += v[d[st]];
}
   out<<s;
    return 0;
}