#include<iostream>
#include<cmath>
#include<cstring>
#include<iomanip>
#include<algorithm>
#include<map>
#include<set>
#include<deque>
#include<queue>
#include<stack>
#include<string>
#include<vector>
#include<utility>
#include<unordered_map>
#define endl '\n'
#define int long long
using namespace std;
const int N=1e6+10;
int f[N];
int tmp[N];
void solve()
{
    int n,m;
    cin >> n >> m;
    for(int i=1;i<=n;i++)
    {
        cin >> f[i];
        tmp[i]=tmp[i-1]+f[i];
    }
    int ans=-1e18;
    for(int i=0;i<=n-m;i++)
    {
        ans=max(ans,tmp[i+m]-tmp[i]);
    }
    cout << (int)(1000*ans/m) << endl;
}
signed main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    // freopen("test.in", "r", stdin);
    // int o;
    // cin >> o;
    // while(o--)
    solve();
    return 0;
}
//
//⠀⠀⠀             ⠀⢸⣿⣿⣿⠀⣼⣿⣿⣦⡀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠀⠀⠀ ⠀⢸⣿⣿⡟⢰⣿⣿⣿⠟⠁
//⠀⠀⠀⠀⠀⠀⠀⢰⣿⠿⢿⣦⣀⠀⠘⠛⠛⠃⠸⠿⠟⣫⣴⣶⣾⡆⠀⠀⠀
//⠀⠀⠀⠀⠀⠀⠀⠸⣿⡀⠀⠉⢿⣦⡀⠀⠀⠀⠀⠀⠀⠛⠿⠿⣿⠃⠀⠀⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⠙⢿⣦⠀⠀⠹⣿⣶⡾⠛⠛⢷⣦⣄⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣧⠀⠀⠈⠉⣀⡀⠀⠀⠙⢿⡇
//⠀⠀⠀⠀⠀⠀⢀⣠⣴⡿⠟⠋⠀⠀⢠⣾⠟⠃⠀⠀⠀⢸⣿⡆
//⠀⠀⠀⢀⣠⣶⡿⠛⠉⠀⠀⠀⠀⠀⣾⡇⠀⠀⠀⠀⠀⢸⣿⠇
//⢀⣠⣾⠿⠛⠁⠀⠀⠀⠀⠀⠀⠀⢀⣼⣧⣀⠀⠀⠀⢀⣼⠇ 
//⠈⠋⠁⠀⠀⠀⠀⠀⠀⠀⠀⢀⣴⡿⠋⠙⠛⠛⠛⠛⠛⠁
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣾⡿⠋⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⢾⠿⠋⠀
//