import java.io.*;
import java.util.*;
import java.util.stream.LongStream;

public class Main {
    private static InputStream is;
    private static PrintWriter out;
    private static String INPUT = "";

    long min(long... o) {
        return LongStream.of(o).min().getAsLong();
    }

    long max(long... o) {
        return LongStream.of(o).max().getAsLong();
    }

    void solve() {
        int n = ni(), a[] = na(n);
        long s[] = new long[n + 1];
        for (int i = 0; i < n; ++i) {
            s[i + 1] = s[i] + a[i];
        }
        long x = Long.MAX_VALUE;
        for (int i = 2; i < n - 1; ++i) {
            int j, k;
            class C {
                long calc(int x, int y, int z) {
                    return Math.abs((s[y] - s[x]) - (s[z] - s[y]));
                }
            }
            C c = new C();
            {
                int min = 1, max = i;
                while (max - min > 1) {
                    int t = (max + min) / 2;
                    long v1 = s[t] - s[0];
                    long v2 = s[i] - s[t];
                    if (v1 <= v2) {
                        min = t;
                    } else {
                        max = t;
                    }
                }
                j = c.calc(0, min, i) < c.calc(0, max, i) ? min : max;
            }
            {
                int min = i + 1, max = n;
                while (max - min > 1) {
                    int t = (max + min) / 2;
                    long v1 = s[t] - s[i];
                    long v2 = s[n] - s[t];
                    if (v1 <= v2) {
                        min = t;
                    } else {
                        max = t;
                    }
                }
                k = c.calc(i, min, n) < c.calc(i, max, n) ? min : max;
            }
            long v1 = s[j] - s[0];
            long v2 = s[i] - s[j];
            long v3 = s[k] - s[i];
            long v4 = s[n] - s[k];
            x = Math.min(x, max(v1, v2, v3, v4) - min(v1, v2, v3, v4));
        }
        out.println(x);
    }

    public static void main(String[] args) throws Exception {
        long S = System.currentTimeMillis();
        is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
        out = new PrintWriter(System.out);

        new Main().solve();
        out.flush();
        long G = System.currentTimeMillis();
        tr(G - S + " ms");
    }

    private static boolean eof() {
        if (lenbuf == -1) return true;
        int lptr = ptrbuf;
        while (lptr < lenbuf)
            if (!isSpaceChar(inbuf[lptr++])) return false;

        try {
            is.mark(1000);
            while (true) {
                int b = is.read();
                if (b == -1) {
                    is.reset();
                    return true;
                } else if (!isSpaceChar(b)) {
                    is.reset();
                    return false;
                }
            }
        } catch (IOException e) {
            return true;
        }
    }

    private static byte[] inbuf = new byte[1024];
    static int lenbuf = 0, ptrbuf = 0;

    private static int readByte() {
        if (lenbuf == -1) throw new InputMismatchException();
        if (ptrbuf >= lenbuf) {
            ptrbuf = 0;
            try {
                lenbuf = is.read(inbuf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (lenbuf <= 0) return -1;
        }
        return inbuf[ptrbuf++];
    }

    private static boolean isSpaceChar(int c) {
        return !(c >= 33 && c <= 126);
    }

    private static int skip() {
        int b;
        while ((b = readByte()) != -1 && isSpaceChar(b))
            ;
        return b;
    }

    private static double nd() {
        return Double.parseDouble(ns());
    }

    private static char nc() {
        return (char) skip();
    }

    private static String ns() {
        int b = skip();
        StringBuilder sb = new StringBuilder();
        while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != ' ')
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    private static char[] ns(int n) {
        char[] buf = new char[n];
        int b = skip(), p = 0;
        while (p < n && !(isSpaceChar(b))) {
            buf[p++] = (char) b;
            b = readByte();
        }
        return n == p ? buf : Arrays.copyOf(buf, p);
    }

    private static char[][] nm(int n, int m) {
        char[][] map = new char[n][];
        for (int i = 0; i < n; i++)
            map[i] = ns(m);
        return map;
    }

    private static int[] na(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = ni();
        return a;
    }

    private static long[] nal(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = ni();
        return a;
    }

    private static int ni() {
        int num = 0, b;
        boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
            ;
        if (b == '-') {
            minus = true;
            b = readByte();
        }

        while (true) {
            if (b >= '0' && b <= '9') {
                num = num * 10 + (b - '0');
            } else {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }

    private static long nl() {
        long num = 0;
        int b;
        boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
            ;
        if (b == '-') {
            minus = true;
            b = readByte();
        }

        while (true) {
            if (b >= '0' && b <= '9') {
                num = num * 10 + (b - '0');
            } else {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }

    private static void tr(Object... o) {
        System.err.println(Arrays.deepToString(o));
    }
}

Measured memory_bytes: 63688