// @check-accepted: examples Ntwo VKsmall Nsmall no-limits
// binary search for the answer

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int N;
    long long K;
    cin >> N >> K;
    K *= N;

    long long sum = 0;
    vector<int> v(N);
    for (auto &x : v) {
        cin >> x;
        sum += x;
    }

    if (sum == K) {
        cout << 0 << endl;
        return 0;
    } else if (sum < K) {
        cout << (K - sum + N - 1) / N << endl;
        return 0;
    }

    int bs = 0;
    for (int i = 1 << 29; i; i /= 2) {
        int cur = bs + i;
        long long min_sum = 0;
        for (auto x : v)
            min_sum += max(1, x - cur);
        if (min_sum > K) bs = cur;
    }

    cout << bs + 1 << endl;
    return 0;
}