// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------

fn run() {
    input! {
        n: usize,
        a: [u64; n],
    }
    let mut a = a;
    a.insert(0, 0);
    for i in 1..a.len() {
        a[i] += a[i - 1];
    }
    let x = a;
    let ans = if x.len() % 2 == 0 {
        let mut ok = 0;
        let mut ng = *x.last().unwrap() + 1;
        while ng - ok > 1 {
            let mid = (ok + ng) / 2;
            let mut pos = x[0];
            let mut cnt = 1;
            for x in x.iter() {
                if *x >= pos + mid {
                    cnt += 1;
                    pos = *x;
                }
            }
            if cnt >= 2 + (x.len() - 2) / 2 {
                ok = mid;
            } else {
                ng = mid;
            }
        }
        ok
    } else {
        let n = x.len() / 2;
        let mut ans = 0;
        let mut x = x;
        for _ in 0..2 {
            let inf = std::u64::MAX / 5;
            let mut stack = vec![inf];
            for i in 0..n {
                let w = x[i + n] - x[i];
                let v = w.min(*stack.last().unwrap());
                stack.push(v);
            }
            let mut min = std::u64::MAX;
            ans = ans.max(min.min(*stack.last().unwrap()));
            for i in 0..n {
                stack.pop();
                let w = x[2 * n - i] - x[n - 1 - i];
                min = min.min(w);
                ans = ans.max(min.min(*stack.last().unwrap()));
            }
            x.reverse();
            let v = x[0];
            for x in x.iter_mut() {
                *x = v - *x;
            }
        }
        ans
    };
    println!("{}", ans);
}

fn main() {
    run();
}