#include <iostream>
#include <fstream>
#include <iomanip>
#include <climits>
#include <limits>
#include <algorithm>
#include <array>
#include <vector>
#include <deque>
#include <queue>
#include <list>
#include <stack>
#include <string>
#include <functional>
#include <numeric>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <unordered_map>
#include <random>
#include <cmath>
#include <complex>
// #include "utiltime.hpp"

using namespace std;

typedef long long int ll;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef complex<double> cdouble;

const int INFL = (int)1e9;
const ll INFLL = (ll)1e18;
const double INFD = numeric_limits<double>::infinity();
const double PI = 3.14159265358979323846;
#define Loop(i, n) for(int i = 0; i < (int)n; i++)
#define Loopll(i, n) for(ll i = 0; i < (ll)n; i++)
#define Loop1(i, n) for(int i = 1; i <= (int)n; i++)
#define Loopll1(i, n) for(ll i = 1; i <= (ll)n; i++)
#define Loopr(i, n) for(int i = (int)n - 1; i >= 0; i--)
#define Looprll(i, n) for(ll i = (ll)n - 1; i >= 0; i--)
#define Loopr1(i, n) for(int i = (int)n; i >= 1; i--)
#define Looprll1(i, n) for(ll i = (ll)n; i >= 1; i--)
#define Loopdiag(i, j, h, w, sum) for(int i = ((sum) >= h ? h - 1 : (sum)), j = (sum) - i; i >= 0 && j < w; i--, j++)
#define Loopdiagr(i, j, h, w, sum) for(int j = ((sum) >= w ? w - 1 : (sum)), i = (sum) - j; j >= 0 && i < h; j--, i++)
#define Loopdiagsym(i, j, h, w, gap) for (int i = ((gap) >= 0 ? (gap) : 0), j = i - (gap); i < (h) && j < (w); i++, j++)
#define Loopdiagsymr(i, j, h, w, gap) for (int i = ((gap) > (h) - (w) - 1 ? (h) - 1 : (w) - 1 + (gap)), j = i - (gap); i >= 0 && j >= 0; i--, j--)
#define Loopitr(itr, container) for(auto itr = container.begin(); itr != container.end(); itr++)
#define printv(vector) Loop(extra_i, vector.size()) { cout << vector[extra_i] << " "; } cout << endl;
#define printmx(matrix) Loop(extra_i, matrix.size()) { Loop(extra_j, matrix[extra_i].size()) { cout << matrix[extra_i][extra_j] << " "; } cout << endl; }
#define quickio() ios::sync_with_stdio(false); cin.tie(0);
#define readfile(filename) ifstream in(filename); cin.rdbuf(in.rdbuf());
#define bitmanip(m,val) static_cast<bitset<(int)m>>(val)
bool nearlyeq(double x, double y) { return abs(x - y) < 1e-9; }
bool inrange(int x, int t) { return x >= 0 && x < t; }
ll rndf(double x) { return (ll)(x + (x >= 0 ? 0.5 : -0.5)); }
ll floorsqrt(double x) { ll m = (ll)sqrt(x); return m + (m * m <= (ll)(x) ? 0 : -1); }
ll ceilsqrt(double x) { ll m = (ll)sqrt(x); return m + ((ll)x <= m * m ? 0 : 1); }
ll rnddiv(ll a, ll b) { return (a / b + (a % b * 2 >= b ? 1 : 0)); }
ll ceildiv(ll a, ll b) { return (a / b + (a % b == 0 ? 0 : 1)); }
ll gcd(ll m, ll n) { if (n == 0) return m; else return gcd(n, m % n); }

/*******************************************************/

int main() {
	quickio();
	int n; cin >> n;
	vll a(n); Loop(i, n) cin >> a[i];
	vll s(n);
	Loop(i, n) {
		if (i == 0) s[i] = a[i];
		else s[i] = s[i - 1] + a[i];
	}
	ll ans = LLONG_MAX;
	ll half = s[n - 1] / 2;
	for (int k = 1; k <= n - 3; k++) {
		ll l_half = s[k] / 2;
		vll l_half_p(4);
		l_half_p[0] = upper_bound(s.begin(), s.begin() + k + 1, l_half) - s.begin();
		l_half_p[1] = l_half_p[0] - 1;
		l_half_p[2] = l_half_p[1] - 1;
		l_half_p[3] = l_half_p[0] + 1;
		Loop(i, 4) {
			if (l_half_p[i] < 0) l_half_p[i] = 0;
			if (l_half_p[i] > k - 1) l_half_p[i] = k - 1;
		}
		ll r_half = s[k] + (s[n - 1] - s[k]) / 2;
		vll r_half_p(4);
		r_half_p[0] = upper_bound(s.begin() + k + 1, s.end(), r_half) - s.begin();
		r_half_p[1] = r_half_p[0] - 1;
		r_half_p[2] = r_half_p[1] - 1;
		r_half_p[3] = r_half_p[0] + 1;
		Loop(i, 4) {
			if (r_half_p[i] < k + 1) r_half_p[i] = k + 1;
			if (r_half_p[i] > n - 1) r_half_p[i] = n - 1;
		}
		Loop(i, 4) {
			Loop(j, 4) {
				vll v = { 
					s[n - 1] - s[r_half_p[j]],
					s[r_half_p[j]] - s[k],
					s[k] - s[l_half_p[i]],
					s[l_half_p[i]]
				};
				ll m = *min_element(v.begin(), v.end());
				ll M = *max_element(v.begin(), v.end());
				ans = min(ans, M - m);
			}
		}
	}
	cout << ans << endl;
}

Measured memory_bytes: 3456