#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,k,a[3000010],l=1,r=1e9,mid;
bool check(int aim){
	int sum=0;
	for(int i=1;i<=n;++i){
		if(a[i]-aim<=0){
			sum=sum+1-(a[i]-aim);
			if(1-(a[i]-aim)>aim){
				return 0;
			}
		}
	}
	if(sum<=aim*k)return 1;
	return 0;
}
signed main() {
	cin>>n>>k;
	for(int i=1;i<=n;++i){
		scanf("%lld",&a[i]);
	}
	while(l<=r){
		mid=(l+r)>>1;
		if(check(mid)){
			l=mid+1;
		}
		else{
			r=mid-1;
		}
	}
   cout<<r;
}