Problem:
Score : 300 points

Problem Statement

Gotou just received a dictionary. However, he doesn't recognize the language used in the dictionary. He did some analysis on the dictionary and realizes that the dictionary contains all possible diverse words in lexicographical order.

A word is called diverse if and only if it is a nonempty string of English lowercase letters and all letters in the word are distinct. For example, atcoder, zscoder and agc are diverse words while gotou and connect aren't diverse words.

Given a diverse word S, determine the next word that appears after S in the dictionary, i.e. the lexicographically smallest diverse word that is lexicographically larger than S, or determine that it doesn't exist.

Let X = x_{1}x_{2}...x_{n} and Y = y_{1}y_{2}...y_{m} be two distinct strings. X is lexicographically larger than Y if and only if Y is a prefix of X or x_{j} > y_{j} where j is the smallest integer such that x_{j} \neq y_{j}.

Constraints

1 \leq |S| \leq 26

S is a diverse word.

Input

Input is given from Standard Input in the following format:

S

Output

Print the next word that appears after S in the dictionary, or -1 if it doesn't exist.

Sample Input 1

atcoder

Sample Output 1

atcoderb

atcoderb is the lexicographically smallest diverse word that is lexicographically larger than atcoder. Note that atcoderb is lexicographically smaller than b.

Sample Input 2

abc

Sample Output 2

abcd

Sample Input 3

zyxwvutsrqponmlkjihgfedcba

Sample Output 3

-1

This is the lexicographically largest diverse word, so the answer is -1.

Sample Input 4

abcdefghijklmnopqrstuvwzyx

Sample Output 4

abcdefghijklmnopqrstuvx

Solution in C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            Scanner cin = new Scanner();
            string S = Console.ReadLine();

            var list = new List<string>();
            for(var x = 'a'; x <= 'z'; x++)
            {
                list.Add(x.ToString());
            }
            foreach(var x in S)
            {
                list.Remove(x.ToString());
            }

            if (list != null) Console.WriteLine(S + list.ElementAt(0));
            else
            {
                if (S == "zyxwvutsrqponmlkjihgfedcba") Console.WriteLine(-1);
                else Console.WriteLine(GetNextPermutation(S));
            }
            Console.ReadLine();
        }

        static string GetNextPermutation(string pTarget)
        {
            var query = pTarget.ToCharArray().OrderBy(X => X);
            string BaseStr = "";
            foreach (char each in query)
            {
                BaseStr += each;
            }

            var stk = new Stack<string>();

            for (int I = 0; I <= BaseStr.Length - 1; I++)
            {
                stk.Push(BaseStr[I].ToString());
            }

            var answerList = new List<string>();

            while (stk.Count > 0)
            {
                string wkStr = stk.Pop();

                if (wkStr.Length == BaseStr.Length)
                {
                    answerList.Add(wkStr);
                    continue;
                }

                for (int I = 0; I <= BaseStr.Length - 1; I++)
                {
                    if (wkStr.Contains(BaseStr[I].ToString()) == false)
                    {
                        stk.Push(wkStr + BaseStr[I].ToString());
                    }
                }
            }

            foreach (string each in answerList.OrderBy(X => X))
            {
                if (pTarget.CompareTo(each) >= 0) continue;
                return each;
            }
            return pTarget;
        }

        static long Factorial(int n) //階乗
        {
            if (n == 1) return 1;
            return n * Factorial(n - 1);
        }

        static long Permutaion(int n, int k) //順列
        {
            long ans = 1;
            for (int i = 0; i < k; i++)
            {
                ans *= (n - i);
            }
            return ans;
        }

        static long Combination(int n, int k) //組み合わせ
        {
            long ans = 1;
            for (int i = n; i > n - k; --i)
            {
                ans = ans * i;
            }
            for (int i = 1; i < k + 1; ++i)
            {
                ans = ans / i;
            }
            return ans;
        }

        static int GCD(int a, int b) //a,bの最大公約数
        {
            if (a < b)
                // 引数を入替えて自分を呼び出す
                return GCD(b, a);
            while (b != 0)
            {
                var remainder = a % b;
                a = b;
                b = remainder;
            }
            return a;
        }

        static int LCM(int a, int b) //a,bの最小公倍数
        {
            return a / GCD(a, b) * b;
        }
    

        static int BinarySearch<T>(T[] array, T target) where T : IComparable<T> //2分探索
        {
            int min = 0;
            int max = array.Length - 1;

            while (true)
            {
                // 範囲内に見つからなかった
                if (max < min) return -1;
                // 範囲内の中央値と比較する
                int mid = min + (max - min) / 2;
                switch (target.CompareTo(array[mid]))
                {
                    case -1:    // 中央値より小さい
                        max = mid - 1;
                        break;
                    case 1:     // 中央値より大きい
                        min = mid + 1;
                        break;
                    case 0:     // 見つかった
                        return mid;
                }
            }
        }

        static void Swap<T>(ref T a, ref T b) //入れ替え
        {
            T tmp = a;
            a = b;
            b = tmp;
        }
    }

    class Scanner //標準入力
    {
        string[] s;
        int i;

        char[] cs = new char[] { ' ' };

        public Scanner()
        {
            s = new string[0];
            i = 0;
        }

        public string next()
        {
            if (i < s.Length) return s[i++];
            string st = Console.ReadLine();
            while (st == "") st = Console.ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            if (s.Length == 0) return next();
            i = 0;
            return s[i++];
        }

        public int Int()
        {
            return int.Parse(next());
        }
        public int[] ArrayInt(int N, int add = 0)
        {
            int[] Array = new int[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = Int() + add;
            }
            return Array;
        }

        public long Long()
        {
            return long.Parse(next());
        }

        public long[] ArrayLong(int N, long add = 0)
        {
            long[] Array = new long[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = Long() + add;
            }
            return Array;
        }

        public double Double()
        {
            return double.Parse(next());
        }


        public double[] ArrayDouble(int N, double add = 0)
        {
            double[] Array = new double[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = Double() + add;
            }
            return Array;
        }
    }
}

/* Dictionaryのvalueが特定の値をとっている要素を削除する
var removeTargetLst = dic.Where(kv => kv.Value == value).ToList();
foreach(var item in removeTargetLst)
{
   dic.Remove(item.Key);
}
*/