//~ how can i make it 10% more fun?
//~ what it would take for me to enjoy this?
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define all(x) x.begin(), x.end()
#define ff first
#define ss second
template <class F, class _S>
bool chmin(F &u, const _S &v){
bool flag = false;
if ( u > v ){
u = v; flag |= true;
}
return flag;
}
template <class F, class _S>
bool chmax(F &u, const _S &v){
bool flag = false;
if ( u < v ){
u = v; flag |= true;
}
return flag;
}
int exp(int x, int n, int m) {
x %= m;
int res = 1;
while (n > 0) {
if (n & 1) { res = (res * x) % m; }
x = (x * x) % m;
n >>= 1;
}
return res;
}
int power(int x, int n) {
int res = 1;
while (n > 0) {
if (n & 1) { res = res * x ; }
x = x * x ;
n >>= 1;
}
return res;
}
const int maxn = 2e5 + 1;
const int mod = 1e9 + 7;
const int inf = 1e18;
void add(int &a, int b) {
if (a + b >= mod) a = (a + b) - mod;
else a += b;
}
void sub(int &a, int b) {
if (a - b < 0) a = (a - b) + mod;
else a -= b;;
}
template<typename T> using matrix = vector<vector<T>>;
namespace FAST {
template<typename T, typename F>
istream &operator>>(istream &cin, pair<T, F> &p) {
cin >> p.first >> p.second;
return cin;
}
template<typename T, typename F>
ostream &operator<<(ostream &cout, pair<T, F> &p) {
cout << p.first << ' ' << p.second;
return cout;
}
template<typename T>
istream &operator>>(istream &cin, vector<T> &a) {
for (T &i: a) cin >> i;
return cin;
}
template<typename T>
ostream &operator<<(ostream &cout, vector<T> &a) {
for (T i: a) cout << i << ' ';
return cout;
}
template<typename T>
istream &operator>>(istream &cin, deque<T> &a) {
for (T &i: a) cin >> i;
return cin;
}
template<typename T>
ostream &operator<<(ostream &cout, deque<T> &a) {
for (T i: a) cout << i << ' ';
return cout;
}
}
using namespace FAST;
void solve() {
int n;
cin >> n;
vector<int> a(n);
cin >> a;
int res = 0;
for(int i = 0;i < n - 1;i++) {
int l = i, r = i + 1;
int now = (a[l] + a[r]) / 2;
while(true) {
int cand1 = -1;
if(l > 0) {
cand1 = a[l - 1];
}
int cand2 = -1;
if(r + 1 < n) {
cand2 = a[r + 1];
}
if(cand1 == -1 && cand2 == -1) {
break;
}
if(cand1 == -1) {
now = (now + cand2) / 2;
r++;
} else if(cand2 == -1) {
now = (now + cand1) / 2;
l--;
} else {
if(cand1 > cand2) {
now = (now + cand2) / 2;
r++;
} else {
now = (now + cand1) / 2;
l--;
}
}
}
chmax(res, now);
}
cout << res;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0),cout.tie(0);
int t = 1;
//~ cin >> t;
while(t--){
solve();
}
}
