#include<cstdio>
#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

bool judge(double val, vector<double> a, const int L) {
    a[0] -= val;
    for(int i = 1; i < a.size(); ++i) a[i] += a[i - 1] - val;
    double res = -1;
    double minv = 0;
    for(int i = L - 1; i < a.size(); ++i) {
        res = max(res, a[i] - minv);
        if(res >= 0) return true;
        minv = min(minv, a[i - L + 1]);
    }
    return res >= 0;
}

int search(const vector<double> &a, const int L) {
    double l = 0, r = 2005;
    double eps = 1e-5;
    while(r - l > eps) {
        double mid = (l + r) / 2;
        if(judge(mid, a, L)) l = mid;
        else r = mid;
    }
    printf("%d\n", (int)(r * 1000)); //在这里打印就不会有错误。
    return (int)(l * 1000);
}


int main() {
    int n, r, v;
    scanf("%d%d", &n, &r);
    vector<double> a;
    for(int i = 0; i < n; ++i) {
        scanf("%d", &v);
        a.push_back(v);
    }

    int d = search(a, r);
    //printf("%d\n", d); 如果在这里打印答案，就会WA，为什么？可以提交一下试试。
}