#include <bits/stdc++.h>

using namespace std;

double inf = 1e18;

const int Nmax = 1e5 + 5;

int a[Nmax];
int n, k, i;
double avg, target_sum, ans = inf, sum = 0;

double get_close(double target, int k)
{
    // return min abs diff between target and a sum that can be obtained by exactly k numbers

    if(k == 0) return abs(target);

    if(k == 1)
    {
        double ans = inf;
        for(int i=1; i<=n; ++i)
            ans = min(ans, abs(a[i] - target));
        return ans;
    }

    set<double> S;
    double ans = inf;

    for(int i=1; i<=n; ++i)
    {
        if(k == 2)
        {
            S.insert(0);
        }
        else if(k == 3)
        {
            if(i>1)
                S.insert(a[i-1]);
        }
        else
        {
            assert(k == 4);
            for(int j=1; j<i-1; ++j)
                S.insert(a[i-1] + a[j]);
        }

        for(int j=i+1; j<=n; ++j)
        {
            double need = target - a[i] - a[j];

            auto it = S.lower_bound(need);

            if(it != S.end())
                ans = min(ans, *it - need);

            if(it != S.begin())
            {
                --it;
                ans = min(ans, need - *it);
            }
        }
    }

    return ans;
}

int main()
{
  //  freopen("input", "r", stdin);
    cin.tie(0); cin.sync_with_stdio(false);

    cin >> n >> k >> avg;
    for(i=1; i<=n; ++i)
    {
        cin >> a[i];
        sum += a[i];
    }

    for(i=0; i<=k; ++i)
    {
        target_sum = sum - (n-i) * avg;
        auto min_abs_diff = get_close(target_sum, i);

        ans = min(ans, min_abs_diff / (n-i));
    }

    cout << setprecision(6) << fixed;
    cout << ans << '\n';

    return 0;
}