#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
using namespace std;
int main()
{
int n, k;
cin >> n >> k;
priority_queue<int, vector<int>, less<int>> qu;
int start;
cin >> start;
int end;
for (int i = 1; i < n; ++i)
{
cin >> end;
qu.push(end - start);
start = end;
}
int tmp;
while (k--)
{
if (qu.top() == 1)
{
break;
}
tmp = qu.top();
qu.pop();
qu.push((tmp + 1) / 2);
qu.push(tmp / 2);
}
cout << qu.top() << endl;
return 0;
}