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

class Program
{
    static int[] dx = new int[] { 0, 0, 1, -1 };
    static int[] dy = new int[] { 1, -1, 0, 0 };
    const int INF = 1010101010;

    static void Solve()
    {
        var s = sc.Str();

        var used = new bool[30];

        if (s == "zyxwvutsrqponmlkjihgfedcba")
        {
            pr.WriteLine(-1);
            return;
        }

        foreach (var c in s)
            used[c - 'a'] = true;

        if (s.Length == 'z' - 'a' + 1)
        {
            for (var i = s.Length - 2; 0 <= i; i--)
            {
                if (s[i] < s[i + 1])
                {
                    pr.Write(s.Substring(0, i));
                    pr.WriteLine((char)s.Substring(i + 1).Where(c => s[i] < c).Min());
                    break;
                }
            }
        }
        else
        {
            pr.Write(s);
            pr.WriteLine((char)('a' + Array.IndexOf(used, false)));
        }
    }

    class Node : IComparable
    {
        public int Id;
        public int Cost;

        public int CompareTo(object obj)
        {
            return ((Node)obj).Cost - Cost;
        }

        public override string ToString()
        {
            return $"Id: {this.Id} - Cost: {this.Cost}";
        }
    }

    class Edge
    {
        public int To;
        public int Cost;
    }

    static double F(double prev, double next, double t)
    {
        return Math.Pow(Math.Exp((next - prev) / t), 2);
    }

    static int[,] Mul(int[,] a, int[,] b)
    {
        var ret = new int[a.GetLength(0), b.GetLength(1)];
        for (int i = 0; i < a.GetLength(0); i++)
            for (int j = 0; j < b.GetLength(1); j++)
                for (int k = 0; k < a.GetLength(1); k++)
                    ret[i, j] += a[i, k] * b[k, j];

        return ret;
    }

    static int[,] Pow(int[,] a, int n)
    {
        var b = new int[a.GetLength(1), a.GetLength(0)];

        var f = n % 2 == 1;

        for (int i = 0; i < a.GetLength(0); i++)
            b[i, i] = 1;

        while (n > 0)
        {
            if (n % 2 == 1)
                b = Mul(a, b);


            n >>= 1;
        }

        return b;
    }

    class Coord
    {
        public int x;
        public int y;
    }

    static void Main(string[] args)
    {
        pr.AutoFlush = true;
        Solve();
        pr.Flush();
        // Console.ReadKey();
    }

    static Scanner sc = new Scanner();
    static Printer pr = new Printer();
}

class Heap<T> where T : IComparable
{
    private List<T> _heap;
    private int _last;
    private int _cnt;
    private IComparer<T> _comparer;

    public Heap()
    {
        _heap = new List<T>();
        _last = 0;
    }

    public Heap(IEnumerable<T> e)
    {
        _heap = new List<T>(e);
        _cnt = _last = _heap.Count();

        for (int i = _last / 2; 0 <= i; i--)
            Heapify(i);
    }

    public Heap(IComparer<T> comparer)
    {
        _comparer = comparer;
    }

    public Heap(IEnumerable<T> e, IComparer<T> comparer) : this(e)
    {
        _comparer = comparer;
    }

    private int Compare(T a, T b)
    {
        if (_comparer == null)
            return a.CompareTo(b);
        else
            return _comparer.Compare(a, b);
    }

    public bool Empty()
    {
        return _last == 0;
    }

    public void Enqueue(T item)
    {
        if (_last < _cnt)
        {

            _heap[_last++] = item;
        }
        else
        {
            _heap.Add(item);
            _cnt++;
            _last++;
        }

        var i = _last - 1;

        while (0 < i)
        {
            if (0 <= Compare(_heap[(i - 1) / 2], _heap[i]))
                break;
            swap((i - 1) / 2, i);
            i = (i - 1) / 2;
        }
    }

    public T Dequeue()
    {
        if (_last == 0)
            throw new Exception("Empty");

        var ret = _heap[0];
        _heap[0] = _heap[--_last];

        Heapify(0);

        return ret;
    }

    public T Peek()
    {
        return _heap[0];
    }

    public int Count()
    {
        return _last;
    }

    private void Heapify(int i)
    {
        var max = i;
        if (i * 2 + 1 < _last && Compare(_heap[max], _heap[i * 2 + 1]) < 0)
            max = i * 2 + 1;
        if (i * 2 + 2 < _last && Compare(_heap[max], _heap[i * 2 + 2]) < 0)
            max = i * 2 + 2;

        if (max == i)
            return;

        swap(i, max);

        Heapify(max);
    }

    private void swap(int a, int b)
    {
        var t = _heap[a];
        _heap[a] = _heap[b];
        _heap[b] = t;
    }
}

#region IO
class Scanner
{
    private int _i = 0;
    private string[] line = new string[0];

    private T[] Enumerate<T>(int n, Func<T> f)
    {
        T[] ret = new T[n];
        for (int i = 0; i < n; i++)
            ret[i] = f();
        return ret;
    }

    public string Str()
    {
        if (line.Length <= _i)
        {
            line = Console.ReadLine().Split(' ');
            _i = 0;
        }

        return line[_i++];
    }

    public int Int() => int.Parse(Str());
    public long Long() => long.Parse(Str());
    public double Double() => double.Parse(Str());
    public int[] Int(int n) => Enumerate(n, Int);
    public long[] Long(int n) => Enumerate(n, Long);
    public double[] Double(int n) => Enumerate(n, Double);
    public string[] Str(int n) => Enumerate(n, Str);
}

class Printer : StreamWriter
{
    public Printer() : base(Console.OpenStandardOutput())
    {
        AutoFlush = false;
    }
}
#endregion

Measured memory_bytes: 13396