#include <iostream>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <utility>
#include <functional>
#include <iomanip>
#include <typeinfo>
#include <iterator>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <tuple>
#include <map>
#include <set>
#include <numeric>
using namespace std;

#define all(container) container.begin(), container.end()
#define sortall(container) (sort(container.begin(), container.end()))
#define yn(cond) ((cond) ? (cout << "Yes" << endl) : (cout << "No" << endl))
#define YN(cond) ((cond) ? (cout << "YES" << endl) : (cout << "NO" << endl))
#define LLONG_MAX numeric_limits<long long>::max()
#define INT_MAX numeric_limits<int>::max()

typedef long long       ll;
typedef vector<int>     vi;
typedef vector<ll>      vll;
typedef vector<double>  vd;
typedef vector<bool>    vb;
typedef vector<string>  vs;
typedef vector<char>    vc;
typedef pair<int, int>  pii;
typedef pair<ll, ll>    pll;
typedef vector<pii>     vpii;
typedef vector<pll>     vpll;
typedef vector<vll>		vvll;
typedef vector<vi>		vvi;
typedef vector<vb>		vvb;
typedef vector<vc>		vvc;

typedef struct edge_ {
	ll to;
	ll cost;
} edge;

typedef struct point_ {
	ll x, y;
} point;

constexpr double	PI = 3.14159265358979323846;
constexpr ll		INF = 1 << 15;
constexpr ll		MOD = (ll)1e9 + 7;
constexpr double	EPS = 1e-7;
constexpr int		dy4[4] = { 0, 1, 0, -1 };
constexpr int		dx4[4] = { 1, 0, -1, 0 };
constexpr int		dy8[8] = { 0, 1, 1, 1, 0, -1, -1, -1 };
constexpr int		dx8[8] = { 1, 1, 0, -1, -1, -1, 0, 1 };

template<typename T>
istream& operator >> (istream& is, vector<T>& vec) {
	for (T& x : vec) is >> x;
	return is;
}

template<typename T>
ostream& operator << (ostream& os, const vector<T>& vec) {
	for (const T& x : vec) os << x << " ";
	return os;
}

template<typename S, typename T>
istream& operator >> (istream& is, pair<S, T>& p) {
	is >> p.first >> p.second;
	return is;
}

istream& operator >> (istream& is, point& p) {
	is >> p.x >> p.y;
	return is;
}

template<typename S, typename T>
ostream& operator << (ostream& os, const pair<S, T>& p) {
	os << "{" << p.first << " " << p.second << "}";
	return os;
}

ostream& operator << (ostream& os, const point& p) {
	os << "(" << p.x << " " << p.y << ")";
	return os;
}


template <typename T>
void say(vector<T>& vec, string pad = " ") {
	for (const T& elem : vec)
		cout << elem << pad;
}


/******************************************************************************/
/**********************         Don't make WA !!         **********************/
/******************************************************************************/


int main()
{
	string S;
	cin >> S;

	map<char, bool> flag;
	for (auto s : S) flag[s] = true;

	if (S.length() < 26) {
		for (int i = 0; i < 26; i++) {
			if (!flag[char('a' + i)]) {
				cout << S << char('a' + i) << endl;
				break;
			}
		}
	}
	else {
		int len = 1;
		for (int i = 1; i < 26; i++) {
			if (S[i - 1] > S[i]) len++;
			else len = 1;
		}

		if (len == 26) {
			cout << -1 << endl;
		}
		else {
			string sub = S.substr(26 - len);
			sortall(sub);
			
			for (int i = 0; i < len; i++)
				if (S[26 - len - 1] < sub[i]) {
					cout << S.substr(0, 26 - len - 1) << sub[i] << endl;
					break;
				}
		}
	}

	return 0;
}

Measured memory_bytes: 256