#ifdef LOCAL111
	#define _GLIBCXX_DEBUG
#else
	#define NDEBUG
#endif
#define _USE_MATH_DEFINES
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <unordered_map>
#include <unordered_set>
#endif
const int INF = 1e9;
using namespace std;
template<typename T, typename U> ostream& operator<< (ostream& os, const pair<T,U>& p) { os << '(' << p.first << ' ' << p.second << ')'; return os; }

#define endl '\n'
#define ALL(a)  (a).begin(),(a).end()
#define SZ(a) int((a).size())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#ifdef LOCAL111
	#define DEBUG(x) cout<<#x<<": "<<(x)<<endl
	template<typename T> void dpite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
#else
	#define DEBUG(x) true
	template<typename T> void dpite(T a, T b){ return; }
#endif
#define F first
#define S second
#define SNP string::npos
#define WRC(hoge) cout << "Case #" << (hoge)+1 << ": "
template<typename T> void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}

typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<int,int> P;

void ios_init(){
	//cout.setf(ios::fixed);
	//cout.precision(12);
#ifdef LOCAL111
	return;
#endif
	ios::sync_with_stdio(false); cin.tie(0);
}

string solve(string);

const int cn = 26;
string naive() {
    vector<string> sv;
    FOR(n, 1, cn+1) {
        string s = "";
        REP(i, n) {
            s.push_back('a'+i);
        }
        do {
            sv.push_back(s);
        }while(next_permutation(ALL(s)));
    }
    sort(ALL(sv));
    dpite(ALL(sv));
    REP(i, SZ(sv)-1) {
        if(solve(sv[i]) != sv[i+1]) {
            DEBUG(solve(sv[i]));
            DEBUG(sv[i+1]);
            cout << sv[i] << endl;
        }
    }
}

string solve(string s) {
    if(SZ(s) < cn) {
        vector<bool> v(cn, false);
        REP(i, SZ(s)) {
            v[s[i]-'a'] = true;    
        }
        REP(i, SZ(v)) {
            if(!v[i]) {
                s.push_back(i+'a');
                break;
            }
        }
        return s;
    } else {
        int nn = -1;
        while(nn == -1 and SZ(s) > 0) {
            vector<bool> v(cn, false);
            char ba = s[SZ(s)-1];
            s.pop_back();
            DEBUG(s);
            DEBUG(ba);
            REP(i, SZ(s)) {
                v[s[i]-'a'] = true;
            }
            dpite(ALL(v));
            FOR(i, ba-'a'+1, SZ(v)) {
                if(!v[i]) {
                    nn = i; 
                    break;
                }
            }
        }
        if(nn == -1) {
            return "-1";
        } else {
            s.push_back(nn+'a');
            return s;
        }
    }
}

int main()
{
	ios_init();
	// naive();
    // solve("abc");
    string s;
    while(cin >> s){
        cout << solve(s) << endl;
    }
	return 0;
}


Measured memory_bytes: 256