o58_oct_c1_evergreen

#include <bits/stdc++.h>

using namespace std;
using lli = long long;
const lli INF = 1e10;
const lli N = 1e3 + 10;
lli ar[N];
lli n, k;

lli Area(lli l, lli r){
    lli base = r - l + 1;
    if(base <= 0) return 0;
    if(base % 2 != 0) return (base + 1) * (base + 1) / 4;
    return base * (base + 2) / 4;
}

bool check(lli x){
    lli sum = 0;
    for(int i=1;i<=n;i++){
        lli area = Area(ar[i] - x, ar[i] + x);
        lli overlap = i + 1 <= n ? Area(ar[i+1] - x, ar[i] + x): 0;
        sum += area - overlap;
    }
    return sum >= k;
}

int main(){

    scanf("%lld%lld", &n, &k);

    for(lli i=1;i<=n;i++)
        scanf("%lld", &ar[i]);

    sort(ar + 1, ar + n + 1);

    lli l = 0, r = INF, ans = INF;
    while(l <= r){
        lli mid = (l + r) / 2;
        bool ch = check(mid);
        if(ch) r = mid - 1, ans = min(ans, mid);
        else l = mid + 1;
    }

    printf("%lld", ans);

    return 0;
}