#include <bits/stdc++.h>
#define cs const
#define pb push_back
using namespace std;

cs int N = 2e5 + 5; 

int n, k; 
int a[N];

void cmx(int & x, int y) {
    if(x < y) x = y; 
}
int mx[N], m;
void add(int x, int v) {
    ++ x; 
    for(; x <= m; x += x & -x) cmx(mx[x], v);
}
int ask(int x) {
    ++ x; 
    int c = -1e9;
    for(; x; x -= x & -x) cmx(c, mx[x]);
    return c; 
}

bool check(double C) {
    static double b[N], c[N];
    for(int i = 1; i <= n; i++) b[i] = a[i] - C; 
    for(int i = 1; i <= n; i++) b[i] += b[i - 1]; 
    for(int i = 1; i <= n; i++) c[i] = b[i];
    // cout << C << endl;
    // for(int i = 1; i <= n; i++) cout << b[i] << ' '; cout << endl;
    c[n + 1] = 0; 
    m = n + 1; 
    sort(c + 1, c + m + 1);
    m = unique(c + 1, c + m + 1) - c - 1; 
    vector <int> f(n + 1, -1e9); 
    f[0] = 0; 
    memset(mx, -0x3f, sizeof mx);
    add(lower_bound(c + 1, c + m + 1, 0) - c, 0); 
    // for(int i = 1; i <= m; i++) cout << c[i] << ' '; cout << endl;
    // cout << lower_bound(c + 1, c + m + 1, 0) - c << endl;
    for(int i = 1; i <= n; i++) {
        b[i] = lower_bound(c + 1, c + m + 1, b[i]) - c; 
        f[i] = ask(b[i]) + 1; 
        add(b[i], f[i]);
        // cout << b[i] << ' ' << f[i] << endl;
    }
    return f[n] >= k; 
}
int main() {
    #ifdef zqj
    freopen("1.in","r",stdin);
    #endif
    ios :: sync_with_stdio(0), cin.tie(0);
    cin >> n >> k; 
    double L = 1e4, R = 0; 
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
        L = min(L, (double) a[i]);
        R = max(R, (double) a[i]);
    }
    for(int T = 0; T <= 30; T++) {
        double mid = (L + R) * 0.5;
        if(check(mid)) L = mid;
        else R = mid; 
    }
    printf("%.10lf\n", L);
    return 0; 
}