二分10分求调

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int maxn = 1e6 + 5;
int n, k;
int a[maxn];
int ans;
inline bool check(int x)
{
	int res = 0;
	for(int i = 1; i <= n; i++)
		res += max(0ll, x - a[i] + 1ll);
	return res <= x * k;
}
signed main()
{
	cin >> n >> k;
	for(int i = 1; i <= n; i++)
		cin >> a[i];
	int l = 0, r = 1e18;
	while(l <= r)
	{
		int mid = (l + r) >> 1;
		if(check(mid))
		{
			ans = mid;
			l = mid + 1;
		}
		else
			r = mid - 1;
	}
	cout << ans;
	return 0;
}