use io::*;
use std::cmp::min;

fn main() {
    let con = read_string();
    let mut sc = Scanner::new(&con);

    let n: usize = sc.next();
    let a: Vec<i64> = sc.next_vec(n);

    let mut sum: Vec<i64> = vec![0; n + 1];

    for i in 0..n {
        sum[i + 1] = sum[i] + a[i];
    }

    let mut ans = 0x7fffffffffffffffi64;

    for i in 2..n - 1 {
        let (p, q) = {
            let b = sum[i] - sum[0];

            let mut ok = 0;
            let mut ng = i + 1;

            while ng - ok > 1 {
                let m = ((ok + ng) / 2) as usize;
                if (sum[m + 1] - sum[0]) * 2 < b {
                    ok = m;
                } else {
                    ng = m;
                }
            }

            let p0 = sum[ok + 1] - sum[0];
            let q0 = sum[i] - sum[ok + 1];

            let p1 = sum[ok + 2] - sum[0];
            let q1 = sum[i] - sum[ok + 2];

            // println!("{:?}, {:?}", (p0, q0), (p1, q1));

            if (p0 - q0).abs() < (p1 - q1).abs() {
                (p0, q0)
            } else {
                (p1, q1)
            }
        };

        let (r, s) = {
            let b = sum[n] - sum[i];

            let mut ok = i;
            let mut ng = n + 1;

            while ng - ok > 1 {
                let m = ((ok + ng) / 2) as usize;
                if (sum[m + 1] - sum[i]) * 2 < b {
                    ok = m;
                } else {
                    ng = m;
                }
            }

            let p0 = sum[ok + 1] - sum[i];
            let q0 = sum[n] - sum[ok + 1];

            let p1 = sum[ok + 2] - sum[i];
            let q1 = sum[n] - sum[ok + 2];

            // println!("{:?}, {:?}", (p0, q0), (p1, q1));

            if (p0 - q0).abs() < (p1 - q1).abs() {
                (p0, q0)
            } else {
                (p1, q1)
            }
        };

        let mut v = vec![p, q, r, s];
        v.sort();
        ans = min(ans, v[3] - v[0]);

        // println!("{}: {:?}", i, v);
    }

    println!("{}", ans);
}

//-----

pub mod io {
    use std;
    use std::str::FromStr;

    pub struct Scanner<'a> {
        iter: std::str::SplitWhitespace<'a>,
    }

    impl<'a> Scanner<'a> {
        pub fn new(s: &'a str) -> Scanner<'a> {
            Scanner {
                iter: s.split_whitespace(),
            }
        }

        pub fn next<T: FromStr>(&mut self) -> T {
            let s = self.iter.next().unwrap();
            if let Ok(v) = s.parse::<T>() {
                v
            } else {
                panic!("Parse error")
            }
        }

        pub fn next_vec_len<T: FromStr>(&mut self) -> Vec<T> {
            let n: usize = self.next();
            self.next_vec(n)
        }

        pub fn next_vec<T: FromStr>(&mut self, n: usize) -> Vec<T> {
            (0..n).map(|_| self.next()).collect()
        }
    }

    pub fn read_string() -> String {
        use std::io::Read;

        let mut s = String::new();
        std::io::stdin().read_to_string(&mut s).unwrap();
        s
    }

    pub fn read_line() -> String {
        let mut s = String::new();
        std::io::stdin().read_line(&mut s).unwrap();
        s.trim_right().to_owned()
    }
}


Measured memory_bytes: 10492