Problem:
Score : 600 points

Problem Statement

Snuke has an integer sequence A of length N.

He will make three cuts in A and divide it into four (non-empty) contiguous subsequences B, C, D and E.
The positions of the cuts can be freely chosen.

Let P,Q,R,S be the sums of the elements in B,C,D,E, respectively.
Snuke is happier when the absolute difference of the maximum and the minimum among P,Q,R,S is smaller.
Find the minimum possible absolute difference of the maximum and the minimum among P,Q,R,S.

Constraints

4 \leq N \leq 2 \times 10^5

1 \leq A_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Find the minimum possible absolute difference of the maximum and the minimum among P,Q,R,S.

Sample Input 1

5
3 2 4 1 2

Sample Output 1

2

If we divide A as B,C,D,E=(3),(2),(4),(1,2), then P=3,Q=2,R=4,S=1+2=3.
Here, the maximum and the minimum among P,Q,R,S are 4 and 2, with the absolute difference of 2.
We cannot make the absolute difference of the maximum and the minimum less than 2, so the answer is 2.

Sample Input 2

10
10 71 84 33 6 47 23 25 52 64

Sample Output 2

36

Sample Input 3

7
1 2 3 1000000000 4 5 6

Sample Output 3

999999994

Solution in Rust (1.15.1) (judge verdict: Accepted)

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

fn read<T: std::str::FromStr>() -> T {
    let stdin = stdin();
    let mut buf = String::new();
	stdin.lock().read_line(&mut buf);
	buf.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
	read::<String>().trim().split_whitespace()
        .map(|w| w.parse().ok().unwrap()).collect()
}

fn divide2(s: usize, t: usize, cum: &Vec<i64>) -> Vec<i64> {
    let mut l = s;
    let mut r = t-1;
    let mut m = (l+r) / 2;
    let mut m1 = cum[m] - cum[s-1];
    let mut m2 = cum[t] - cum[m];
    let mut dmin = m1 - m2;
    if dmin == 0 {
        return vec![m1,m2];
    } else if dmin > 0 {
        r = m;
    } else {
        l = m;
    }
    while l + 1 < r {
        m = (l+r) / 2;
        let t1 = cum[m] - cum[s-1];
        let t2 = cum[t] - cum[m];
        let dt = t1 - t2;
        if dmin.abs() > dt.abs() {
            m1 = t1;
            m2 = t2;
            dmin = dt;
        }
        if dt == 0 {
            return vec![m1,m2];
        } else if dt > 0 {
            r = m;
        } else {
            l = m;
        }
    }
    let t1 = cum[l] - cum[s-1];
    let t2 = cum[t] - cum[l];
    let dt = t1 - t2;
    if dmin.abs() > dt.abs() {
        m1 = t1;
        m2 = t2;
        dmin = dt;
    }
    let t1 = cum[r] - cum[s-1];
    let t2 = cum[t] - cum[r];
    let dt = t1 - t2;
    if dmin.abs() > dt.abs() {
        m1 = t1;
        m2 = t2;
    }
    return vec![m1,m2];
}

fn main() {
    let n = read::<usize>();
    let a = read_vec::<i64>();
    let mut cum: Vec<i64> = vec![0;n+1];
    for i in 0..n {
        cum[i+1] = cum[i] + a[i];
    }
    let mut ans = -1;
    for p in 3..n {
        let m1 = divide2(1,p-1,&cum);
        let m2 = divide2(p,n,&cum);
        let min = cmp::min(cmp::min(m1[0],m1[1]),cmp::min(m2[0],m2[1]));
        let max = cmp::max(cmp::max(m1[0],m1[1]),cmp::max(m2[0],m2[1]));
        if ans < 0 || ans > max - min {
            ans = max - min;
        }
    }
    println!("{}",ans);
}