#include <bits/stdc++.h>
using namespace std;
int n,m,a[1000001],l = 0,r = -1,ans = -1;
bool check(int x){
	long long sum = 0;
	for(int i = 1;i<=n;i++)sum+=max(0,a[i]-x);
	return sum>=m;
}
int main() {
	scanf("%d%d",&n,&m);
	for(int i = 1;i<=n;i++){
		scanf("%d",&a[i]);
		r = max(r,a[i]);
	}
	while(l<=r){
		int mid = l+(r-l)/2;
		if(check(mid)){
			ans = mid;
			l = mid+1;
		}
		else r = mid-1;
	}
	printf("%d",ans);
	return 0;
}