https://www.acmicpc.net/problem/2805
#include <iostream>
#include <vector>
using namespace std;
long long check(vector<long long> v, long long high)
{
long long total = 0;
for (int i = 0; i < v.size(); i++)
{
if (v[i] - high > 0)
total += v[i] - high;
}
return total;
}
int main(void)
{
cin.tie(0);
cout.tie(0);
ios_base::sync_with_stdio(0);
long long N, M, tmp;
vector<long long> v;
long long low = 0, high = 0;
long long answer = 0;
cin >> N >> M;
for (int i = 0; i < N; i++)
{
cin >> tmp;
v.push_back(tmp);
high = max(high, tmp);
}
while (low <= high)
{
long long mid = (low + high) / 2;
if (check(v, mid) >= M)
{
answer = max(answer, mid);
low = mid + 1;
}
else
{
high = mid - 1;
}
}
cout << answer;
return 0;
}