#include <bits/stdc++.h>
using namespace std;

#define ff first
#define ss second
#define bl ' '
#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define comp(v) (v).erase(unique(all(v)), (v).end())

typedef long long ll;
typedef pair<int, int> pi;
typedef pair<pi, int> pii;
typedef pair<pi, pi> pipi;
typedef pair<ll, ll> pll;

const int MAXN = 300300;
const int MOD = 998244353;
const int INF = 1e9;

ll arr[MAXN], dp[MAXN];
vector<ll> v, tree;
int n, k;

void update(int node, int s, int e, int idx, ll val) {
    if(e < idx || idx < s) return;
    if(s == e) {
        tree[node] = max(tree[node], val);
        return;
    }

    int mid = s+e>>1;
    update(node<<1, s, mid, idx, val); update(node<<1|1, mid+1, e, idx, val);
    tree[node] = max(tree[node<<1], tree[node<<1|1]);
}

ll solve(int node, int s, int e, int l, int r) {
    if(e < l || r < s) return LLONG_MIN;
    if(l <= s && e <=r) return tree[node];

    int mid = s+e>>1;
    return max(solve(node<<1, s, mid, l, r), solve(node<<1|1, mid+1, e, l, r));
}

bool chk(int mid) {
    if(arr[n]*100000 < n*mid) return false;

    v.clear();
    for(int i = 0; i <= n; i++) {
        v.push_back(100000*arr[i]-i*mid);
    }

    sort(all(v)); comp(v);

    int sz = v.size();
    tree.clear(); tree.resize(4*sz, LLONG_MIN);

    dp[0] = 0;
    int x = lower_bound(all(v), 100000*arr[0]-0*mid)-v.begin();
    update(1, 0, sz-1, x, dp[0]);
    for(int i = 1; i <= n; i++) {
        x = lower_bound(all(v), 100000*arr[i]-i*mid)-v.begin();

        dp[i] = LLONG_MIN;
        ll t = solve(1, 0, sz-1, 0, x);//cout<<t<<bl;
        if(t != LLONG_MIN) dp[i] = t+1;

        update(1, 0, sz-1, x, dp[i]);//cout<<dp[i]<<endl;
    }

    return dp[n] >= k;
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);

    cin >> n >> k;
    for(int i = 1; i <= n; i++) {
        cin >> arr[i];
        arr[i] += arr[i-1];
    }//return chk(1);

    int lb = 0, ub = 1000*100000, mid;
    while(lb < ub) {
        mid = lb+ub+1>>1;
        if(chk(mid)) lb = mid;
        else ub = mid-1;
    }

    cout << (double)lb/100000;
}