#include <iostream>
#include <cstdio>

using namespace std;

int arr[100005];
double sum[100005];
int n, F;

bool fun(double aver) {
    for(int i = 1; i <= n; i++) {
        sum[i] = sum[i - 1] + arr[i] - aver;    
    }
    double minn = 1e9, ans = -1e9;
    for(int i = F; i <= n; i++) {
        minn = min(minn, sum[i - F]);       
        ans = max(ans, sum[i] - minn);
    }
    return ans >= 0;
}

int main() {
    scanf("%d %d", &n, &F);
    for(int i = 1; i <= n; i++) {
        scanf("%d", &arr[i]);
    }
    double l = -1e6, r = 1e6;
    while(r - l > 1e-5) {
        double mid = (l + r) / 2.0;
        if(fun(mid)) {
            l = mid;
        } else {
            r = mid;
        }
    }
    cout << (long long)(r * 1000) << endl;
    return 0;
}