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

bool f(ll x, ll k, vector<ll> arak) {
	ll cel = arak.size() * k;
	for(int i = 0; i < arak.size(); i++) {
		cel -= arak[i];
	}
	for(int i = 0; i < arak.size(); i++) {
		if(cel > 0) cel -= min(cel, x);
		else if(cel < 0) cel += min(abs(cel), min(arak[i] - 1, x));
	}
	return cel == 0;
}

int main() {
	ll n, k;
	cin >> n >> k;

	vector<ll> arak(n);

	for(int i = 0; i < n; i++) {
		cin >> arak[i];
	}

	ll l = 0, r = 1e10;
	while(l < r - 1) {
		ll kozep = (l + r) / 2;
		if(f(kozep, k, arak)) {
			r = kozep;
		} else {
			l = kozep;
		}
	}

	cout << r << endl;
	
	return 0;
}