#include <iostream>
#include <vector>
#include <stdio.h>
using namespace std;

int min(vector <int> q){
    int m=q[0];
    if (m>q[1]) m=q[1];
    if (m>q[2]) m= q[2];
    return m;
}
int main(void)
{
    vector <int> que;
    int i,n,k,x,s=0;

    freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%d %d", &n, &k);
    for (i=1;i<=n;i++ ){
        scanf("%d",&x);
        que.push_back(x);
        if (que.size()>k){
                s += min(que);
                que.erase(que.begin());
        }
    }
    s += min(que);
    printf("%d ", s);
    return 0;
}