using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var S = sc.ReadStr();
        var flag = new bool[26];
        for (int i = 0; i < S.Length; i++)
        {
            flag[S[i] - 'a'] = true;
        }

        for (int i = 0; i < flag.Length; i++)
        {
            if (flag[i] == false)
            {
                var ans = S + (char)(i + 'a');
                Console.WriteLine(ans);
                return;
            }
        }
        if (S == "zyxwvutsrqponmlkjihgfedcba")
        {
            Console.WriteLine("-1");
            return;
        }

        var list = new List<char>();
        list.Add(S[S.Length - 1]);
        for (int i = S.Length - 2; i >= 0; i--)
        {
            if (S[i + 1] > S[i])
            {
                if (list.Exists(x => x > S[i]))
                {
                    var c = list.Where(x => x > S[i]).OrderBy(x => x).First();
                    var ans = S.Substring(0, i) + c;
                    Console.WriteLine(ans);
                    return;
                }
            }
            list.Add(S[i]);
        }
    }

    static int MOD = (int)1e9 + 7;
    static int INF = (int)1e7 + 1;
    static long LINF = (long)1e13 + 1;
    static Scanner sc = new Scanner();
}

class Scanner
{
    string[] S = new string[0];
    int Index = 0;
    char[] Separators = new char[] { ' ' };

    public string Next()
    {
        if (this.Index < this.S.Length) return this.S[this.Index++];
        var line = "";
        while (line == "") line = Console.ReadLine();
        this.S = line.Split(this.Separators, StringSplitOptions.RemoveEmptyEntries);
        if (this.S.Length == 0) return this.Next();
        this.Index = 0;
        return this.S[this.Index++];
    }
    public string ReadStr()
    {
        return this.Next();
    }
    public char ReadChar()
    {
        return this.Next()[0];
    }
    public int ReadInt()
    {
        return int.Parse(this.Next());
    }
    public uint ReadUInt()
    {
        return uint.Parse(this.Next());
    }
    public long ReadLong()
    {
        return long.Parse(this.Next());
    }
    public double ReadDouble()
    {
        return double.Parse(this.Next());
    }
    public int[] ReadIntArray(int n)
    {
        var array = new int[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadInt();
        }
        return array;
    }
    public long[] ReadLongArray(int n)
    {
        var array = new long[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadLong();
        }
        return array;
    }
    public double[] ReadDoubleArray(int n)
    {
        var array = new double[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadDouble();
        }
        return array;
    }
    public char[] ReadCharArray(int n)
    {
        var array = new char[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadChar();
        }
        return array;
    }
    public string[] ReadStrArray(int n)
    {
        var array = new string[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadStr();
        }
        return array;
    }
}


Measured memory_bytes: 11476