#include <bits/stdc++.h>
using namespace std;
template <typename T> void read(T &x) {
	x = 0;
	bool w = false;
	char c = getchar();
	while (~c && !isdigit(c)) w |= c == '-', c = getchar();
	while (isdigit(c)) x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();
	if (w) x = -x;
}
template <typename T> void write(T x) {
	static int stk[24];
	int top = 0;
	while (x) {
		stk[++ top] = x % 10;
		x /= 10;
	}
	while (top) putchar(stk[top --] + 48);
	putchar(' ');
}
const double eps = 1e-5;
const int N = 1e5 + 2;
double l = 1e9, r = -1e9, sum[N];
int n, t, a[N];
bool check(double f) {
	double mi = 1e9;
	for (int i = 1; i <= n; i ++)
		sum[i] = sum[i - 1] + a[i] - f;
	for (int i = t; i <= n; i ++) {
		mi = min(mi, sum[i - t]);
		if (sum[i] - mi >= 0) return true;
	}
	return false;
}
int main() {
	read(n), read(t);
	for (int i = 1; i <= n; i ++)
		read(a[i]), l = min(l, (double)a[i]), r = max(r, (double)a[i]);
	for (double mid = (l + r) / 2.0; fabs(r - l) > eps; mid = (l + r) / 2.0)
		check(mid) ? l = mid : r = mid;
	write((int)floor(r * 1000)); // 警示后人，精度误差，只能写r
	return 0;
}