#include <bits/stdc++.h>

using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");

deque <int> q;
int n,k,x,minn,s;

int main()
{
    in>>n>>k;
    for(int i=1;i<=n;i++){
        in>>x;
        q.push_back(x);
    }
    for(int i=0;i<n;i++){
            minn=q[i];
        for(int it=i+1;it<k+i;it++){
            if(q[it] < minn){
                minn=q[it];
            }
        }

        s+=minn;
    }
    out<<s;

    return 0;
}