#include <bits/stdc++.h>
#define pb push_back
#define pi pair<int, int>
#define l first
#define r second
#define all(x) x.begin(), x.end()

const int maxn = 5e5 + 1;

using namespace std;

int n;
string s;

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    string s; cin >> s;
    int n = s.size();
    bitset<26> bt;
    if (n < 26) {
        for (int i = 0; i < n; i++)
            bt[s[i] - 'a'] = 1;
        cout << s;
        for (int x = 0; x < 26; x++)
            if (!bt[x]) {
                cout << (char)(x + 'a');
                break;
            }
        return 0;
    }
    for (int i = n - 1; i >= 0; i--) {
        bool fg = 0;
        for (char j = s[i] + 1; j <= 'z'; j++) {
            fg = 1;
            for (int l = 0; l < i; l++) {
                if (s[l] == j) {
                    fg = 0;
                    break;
                }
            }
            if (!fg) continue;
            s[i] = j;
            cout << s.substr(0, i + 1);
            return 0;
        }
    }
    cout << -1;
    return 0;
}

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<cmath>
#include<bitset>
#include<deque>
#include<functional>
#include<iterator>
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<utility>
using namespace std;
typedef long long ll;
#define a first
#define b second
#define sz(x) (ll)((x).size())
#define pb push_back
#define mp make_pair
#define bg begin()
#define ed end()
#define all(x) (x).bg,(x).ed
#define rep(i,n) for(ll i=0;i<(n);i++)
#define rep1(i,n) for(ll i=1;i<=(n);i++)
#define rrep(i,n) for(ll i=(n)-1;i>=0;i--)
#define rrep1(i,n) for(ll i=(n);i>=1;i--)
#define FOR(i,a,b) for(ll i=(a);i<(b);i++)
const ll MOD=1000000007;
const ll INF=1000000000000000;
template<class T> inline bool chmin(T& a, T b){if(a>b){a=b;return true;}return false;}
template<class T> inline bool chmax(T& a, T b){if(a<b){a=b;return true;}return false;}
ll maxx(ll x,ll y,ll z){return max(max(x,y),z);}
ll minn(ll x,ll y,ll z){return min(min(x,y),z);}
ll gcd(ll x,ll y){if(x%y==0) return y;else return gcd(y,x%y);}
ll lcm(ll x,ll y){return x*(y/gcd(x,y));}
ll digsz(ll x){if(x==0) return 1;else{ll ans=0;while(x){x/=10;ans++;}return ans;}}
ll digsum(ll x){ll sum=0;while(x){sum+=x%10;x/=10;}return sum;}
vector<ll> pw2(62,1);vector<ll> pw10(19,1);

int main(){
    {rep1(i,61) pw2[i]=2*pw2[i-1];}
    {rep1(i,18) pw10[i]=10*pw10[i-1];}
    
    string s; cin>>s;
    vector<ll> X(26,0);
    rep(i,sz(s)){
        X[(ll)(s[i]-'a')]++;
    }
    
    string t="";
    rrep(i,26){
        t+=('a'+i);
    }
    if(s==t){
        cout<<-1<<endl;
        return 0;
    }
    
    ll tmp=INF;
    rep(i,26){
        if(X[i]==0){
            tmp=i;
            break;
        }
    }
    
    //全文字
    if(tmp==INF){
        ll c;
        vector<ll> Y;
        rrep1(i,sz(s)-1){
            Y.pb((ll)(s[i]-'a'));
            if(s[i]>s[i-1]){
                c=i-1;
                break;
            }
        }
        sort(all(Y));
        rep(i,sz(s)){
            if(c==i){
                ll d=(ll)(s[i]-'a');
                cout<<(char)('a'+*(upper_bound(Y.bg,Y.ed,d)));
                return 0;
            }
            else cout<<s[i];
        }
    }
    else{
        cout<<s<<(char)('a'+tmp)<<endl;
    }
}

