Problem:
Score : 300 points

Problem Statement

Snuke and Raccoon have a heap of N cards. The i-th card from the top has the integer a_i written on it.

They will share these cards.
First, Snuke will take some number of cards from the top of the heap, then Raccoon will take all the remaining cards.
Here, both Snuke and Raccoon have to take at least one card.

Let the sum of the integers on Snuke's cards and Raccoon's cards be x and y, respectively.
They would like to minimize |x-y|.
Find the minimum possible value of |x-y|.

Constraints

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

-10^{9} \leq a_i \leq 10^{9}

a_i is an integer.

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_{N}

Output

Print the answer.

Sample Input 1

6
1 2 3 4 5 6

Sample Output 1

1

If Snuke takes four cards from the top, and Raccoon takes the remaining two cards, x=10, y=11, and thus |x-y|=1. This is the minimum possible value.

Sample Input 2

2
10 -10

Sample Output 2

20

Snuke can only take one card from the top, and Raccoon can only take the remaining one card. In this case, x=10, y=-10, and thus |x-y|=20.

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using static Atcoder;
using System.Threading.Tasks;
using System.ComponentModel;

public class Hello
{
    private const int INF = 1000000007;
    public static void Main()
    {
        int N = IntRead();
        //int N = 2 * (int)Math.Pow(10, 5);
        var ai = SpRead(' ').Select(long.Parse).ToList();
        //List<long> ai = new List<long>();
        //string b = "1000000000";
        //for (int i = 0; i < N; i++) ai.Add(long.Parse(b));
        long Sums = ai.Sum();
        long Sunuke = ai[0];
        long Arai = Sums - Sunuke;
        long ans = Math.Abs(Sunuke - Arai);
        for (int i = 1; i < N - 1; i++)
        {
            Sunuke += ai[i];
            ans = Math.Min(ans, Math.Abs(2 * Sunuke - Sums));
        }
        Console.WriteLine(ans);
    }
}

public class Factorization
{
    private static long N;

    public Factorization(long n) { N = n; }

    //最大公約数を返す
    public static long GCD(long a, long b)
    {
        if (a < b) return GCD(b, a);
        long r;
        while (b != 0)
        {
            r = a % b;
            a = b;
            b = r;
        }
        return a;
    }

    //素数判定
    public static bool IsPrime(long n)
    {
        if (n < 2) return false;
        if (n == 2) return true;
        if (n % 2 == 0) return false;

        double root = Math.Sqrt(n);
        for (int i = 3; i <= root; i += 2)
        {
            if (n % i == 0) return false;
        }
        return true;
    }

    //試し割り
    private static int[] TryPrimes = new int[] { 2, 3, 5, 7, 11 };
    public long TryAllocation(long p)
    {
        long count = 0;
        while (N % p == 0)
        {
            count++;
            N /= p;
        }
        return count;
    }

    private int[] xi = new int[] { 13, 17, 19, 23, 29 };
    private long f(long x, int suffix)
    {
        return (xi[suffix % xi.Count()] * x + suffix) % N;
    }

    //nを分解
    public long PollardsRho(long n, int suffix = 0)
    {
        //素数を渡すと失敗するらしい
        if (IsPrime(n)) return n; //もう素数
        long x = 2, y = 2, d = 1;
        while (d == 1)
        {
            x = f(x, suffix);
            y = f(f(y, suffix), suffix);
            d = GCD(Math.Abs(x - y), n);
        }
        if (d == n)
        {
            //f(x)を変えて試す
            return PollardsRho(n, suffix + 1);
        }
        return d;
    }

    public IEnumerable<long> Calc()
    {
        //小さな素因数の計算
        foreach (var prime in TryPrimes)
        {
            var box = TryAllocation(prime);
            for (int i = 0; i < box; i++) yield return prime;
        }

        //残りをRhoで解く
        while (true)
        {
            if (N == 1) break;
            var ret = PollardsRho(N);
            yield return ret;
            N /= ret;
        }
    }
}


public class Atcoder
{
    static void Swap<T>(ref T a, ref T b)
    {
        var t = a;
        a = b;
        b = t;
    }
    public static int LCM(int a, int b)
    {
        int c = a * b;
        if (a < b) Swap(ref a, ref b);
        int d = a % b;
        while (d != 0)
        {
            a = b;
            b = d;
            d = a % b;
        }
        return c / b;
    }
    public static string StrReverce(string s)
    {
        return new string(s.Reverse().ToArray());
    }
    public static int IntRead()
    {
        return int.Parse(Console.ReadLine());
    }
    public static bool IsPrime(int n)
    {
        if (n < 2) return false;
        if (n == 2) return true;
        if (n % 2 == 0) return false;

        //double sqrtNum = Math.Sqrt(n);
        for (int i = 3; i < n; i += 2)
        {
            if (n % i == 0) return false;
        }
        return true;
    }
    public static string[] SpRead(char c)
    {
        return Console.ReadLine().Split(c);
    }
    public static long[] LSRead()
    {
        return Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
    }
    public static long Combination(int n, int r)
    {
        if (n == r) return 1;
        return
            Enumerable.Range((n - r), r).ToList().Aggregate((now, next) => now * next) /
            Enumerable.Range(1, r).ToList().Aggregate((now, next) => now * next);
    }
    public static long LongRead()
    {
        return long.Parse(Console.ReadLine());
    }
}