#include <bits/stdc++.h>

using namespace std;

FILE *F=fopen("deque.in", "r"), *G=fopen("deque.out", "w");

deque<int> dq;
int n, k, v[5000003], x;
long long s;

int main()
{
    fscanf(F, "%d %d ", &n, &k);
    for(int i = 1; i <= n; ++ i)
    {
        fscanf(F, "%d ", &v[i]);

        while(!dq.empty() && v[dq.back()] >= v[i]) dq.pop_back();

        dq.push_back(i);

        if(dq.front() == i-k) dq.pop_front();

        if(i >= k) s += v[dq.front()];
    }
    fprintf(G, "%lld ", s);
    return 0;
}