#include <iostream>
#include <cmath>
#include <vector>
using namespace std;
int main() {
// your code goes here
vector<int> l, m;
int n, i, diff, temp;
float x, mean;
//cout << "enter list size : ";
cin >> n;
//cout << "enter elements : \n";
mean = 0;
for(i = 0;i < n; ++i){
cin >> temp;
l.push_back(temp);
m.push_back(0);
if(i != n-1)
mean += temp;
}
x = ceil(mean / (n-1));
cout << "ceil of mean = " << x << "\n";
//cout << mean <<"\t";
for(i = ((n-1)/2)-1; i >= 0; --i){
m[i] = --x;
}
x = ceil(mean/(n-1));
x = x-1;
for(i = ((n-1)/2); i < n-1; ++i){
m[i] = ++x;
}
diff = 0;
for(i = 0;i < n-1; ++i){
if(abs(m[i]-l[i]) > diff){
diff = abs(m[i]-l[i]);
//cout << diff << "->" << i+1 <<"\t";
}
}
cout << diff <<"\n";
return 0;
}
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