#[allow(unused_imports)]
use std::char::from_digit;
#[allow(unused_imports)]
use std::cmp::{max, min};
#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
#[allow(unused_imports)]
use std::fs::File;
#[allow(unused_imports)]
use std::io::prelude::*;
#[allow(unused_imports)]
use std::io::{stdin, stdout, BufReader, BufWriter, Stdin, Stdout, Write};
#[allow(unused_imports)]
use std::mem::swap;
#[allow(unused_imports)]
use std::str::FromStr;

type BoxResult<T> = Result<T, Box<std::error::Error>>;


fn main() {
    let mut scanner = Scanner::new(stdin());
    let n = scanner.read::<usize>().unwrap();
    let arr = scanner.read_vector::<i64>().unwrap();
    let mut cumsum = vec![arr[0]];
    for i in 1..n {
        let last = cumsum[i - 1];
        cumsum.push(last + arr[i]);
    }
    let mut minimum = std::i64::MAX;
    let (mut left_index, mut right_index) = (0, 2);
    for i in 1..(n - 2) {
        right_index = max(right_index, i + 1);
        let (mut left_min, mut left_max) = (min(cumsum[left_index], cumsum[i] - cumsum[left_index]), max(cumsum[left_index], cumsum[i] - cumsum[left_index]));
        let (mut right_min, mut right_max) = (min(cumsum[right_index] - cumsum[i], cumsum[n - 1] - cumsum[right_index]), max(cumsum[right_index] - cumsum[i], cumsum[n - 1] - cumsum[right_index]));
        while left_index + 1 < i {
            let l1 = cumsum[left_index + 1];
            let l2 = cumsum[i] - cumsum[left_index + 1];
            if (l2 - l1).abs() < left_max - left_min {
                left_index += 1;
                left_min = min(l1, l2);
                left_max = max(l1, l2);
            } else {
                break;
            }
        }
        while right_index + 1 < n - 1 {
            let r1 = cumsum[right_index + 1] - cumsum[i];
            let r2 = cumsum[n - 1] - cumsum[right_index + 1];
            if (r2 - r1).abs() < right_max - right_min {
                right_index += 1;
                right_min = min(r1, r2);
                right_max = max(r1, r2);
            } else {
                break;
            }
        }
        let diff = max(left_max, right_max) - min(left_min, right_min);
        minimum = min(diff, minimum);
    }

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

#[allow(dead_code)]
struct Scanner<R> {
    reader: BufReader<R>,
    buffer: String,
}
impl<R> Scanner<R>
where
    R: Read,
{
    #[allow(dead_code)]
    fn new(inner: R) -> Scanner<R> {
        let reader = BufReader::new(inner);
        let buffer = String::new();
        Scanner {
            reader: reader,
            buffer: buffer,
        }
    }
    #[allow(dead_code)]
    fn with_capacity(capacity: usize, inner: R) -> Scanner<R> {
        let reader = BufReader::with_capacity(capacity, inner);
        let buffer = String::new();
        Scanner {
            reader: reader,
            buffer: buffer,
        }
    }

    #[allow(dead_code)]
    fn read_line(&mut self) -> BoxResult<String> {
        self.reader.read_line(&mut self.buffer)?;
        let cloned = self.buffer.trim().to_string();
        self.buffer.clear();
        Ok(cloned)
    }

    #[allow(dead_code)]
    fn read<T>(&mut self) -> BoxResult<T>
    where
        T: FromStr,
        T::Err: std::fmt::Debug,
        T::Err: std::error::Error,
        T::Err: 'static,
    {
        self.reader.read_line(&mut self.buffer)?;
        let parsed = self.buffer.trim().parse()?;
        self.buffer.clear();
        Ok(parsed)
    }
    #[allow(dead_code)]
    fn read_vector<T>(&mut self) -> BoxResult<Vec<T>>
    where
        T: FromStr,
        T::Err: std::fmt::Debug,
        T::Err: std::error::Error,
        T::Err: 'static,
    {
        self.reader.read_line(&mut self.buffer)?;
        let parsed_vec = self
            .buffer
            .trim()
            .split_whitespace()
            .map(|s| s.parse())
            .collect::<Result<Vec<_>, _>>()?;
        self.buffer.clear();
        Ok(parsed_vec)
    }
    #[allow(dead_code)]
    fn read_matrix<T>(&mut self, lines: usize) -> BoxResult<Vec<Vec<T>>>
    where
        T: FromStr,
        T::Err: std::fmt::Debug,
        T::Err: std::error::Error,
        T::Err: 'static,
    {
        let mut parsed_matrix = vec![];
        for _ in 0..lines {
            self.reader.read_line(&mut self.buffer)?;
            parsed_matrix.push(
                self.buffer
                    .trim()
                    .split_whitespace()
                    .map(|s| s.parse())
                    .collect::<Result<Vec<_>, _>>()?,
            );
            self.buffer.clear();
        }
        Ok(parsed_matrix)
    }
    #[allow(dead_code)]
    fn read_chars(&mut self) -> BoxResult<Vec<char>> {
        self.reader.read_line(&mut self.buffer)?;
        let chars = self.buffer.trim().chars().collect::<Vec<_>>();
        self.buffer.clear();
        Ok(chars)
    }
}


Measured memory_bytes: 13560