#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <tuple>
#include <cstdint>
#include <cstdio>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <bitset>
#include <cctype>
#include <random>
#include <cassert>
#include <numeric>
#define ll long long int
#define LL unsigned long long
#define pb push_back
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
using namespace std;

int mx8[] = {0,0,1,-1,-1,1,-1,1};
int my8[] = {-1,1,0,0,-1,-1,1,1};
int mx4[] = {1,-1,0,0};
int my4[] = {0,0,-1,1};
const int MOD = 1000000007;

ll y[10000005];

int main() {
    string s; cin >> s;
    int n = s.size();

    map<char,int> mp;
    rep(i,n) mp[s[i]]++;

    rep(i,26){
        if(!mp[char (i+97)]){
            cout << s + char(i+97) << endl;
            return 0;
        }
    }
    if(s == "zyxwvutsrqponmlkjihgfedcba") cout << -1 << endl;
    else {
        for(int i = n-1; i >= 1; i--){
            if(s[i-1] < s[i]){
                rep(j,i-1){
                    cout << s[j];
                }
                for(int j = n-1; j>=1;j--){
                    if(s[i-1] < s[j]){
                        cout << s[j];
                        return 0;
                    }
                }
                return 0;
            }
        }
    }
}

#include<bits/stdc++.h>
//using namespace std;
#define rep(i,j,n) for(ll i=(ll)(j);i<(ll)(n);i++)
#define REP(i,j,n) for(ll i=(ll)(j);i<=(ll)(n);i++)
#define per(i,j,n) for(ll i=(ll)(j);(ll)(n)<=i;i--)
#define ll long long
#define ALL(a) (a).begin(),(a).end()
#define disup(A,key) distance(A.begin(),upper_bound(ALL(A),(ll)(key)))
#define dislow(A,key) distance(A.begin(),lower_bound(ALL(A),(ll)(key)))
#define pb push_back
#define mp std::make_pair
#define endl "\n"
using std::cin;
using std::cout;
using std::vector;
using std::string;
using std::upper_bound;
using std::lower_bound;
using vi=vector<ll>;
using vii=vector<vi>;
using pii=std::pair<ll,ll>;
const ll MOD=1e9+7;
//const ll MOD=998244353;
//const ll MOD=100000;
const ll MAX=1e7;
const ll INF=(1ll<<60);
template<class T>
class prique :public std::priority_queue<T, std::vector<T>, std::greater<T>> {};
struct Binary_indexed_tree{
    int N;
    vi bit;
    Binary_indexed_tree(int n):N(n){
        bit.resize(N+1,0);
    }
    void add(int x,int a){
        for(x;x<=N;x+=(x&-x)) bit[x]+=a;
    }
    ll sum(int x){
        ll ret=0;
        for(x;x>0;x-=(x&-x)) ret+=bit[x];
        return ret;
    }
    ll lower_bound(ll X){
        if(sum(N)<X) return -1;
        ll ret=0,memo=1,sum=0;
        while(memo*2<=N) memo*=2;
        while(memo>0){
            if(memo+ret<=N&&sum+bit[memo+ret]<X){
                sum+=bit[memo+ret];
                ret+=memo;
            }
            memo/=2;
        }
        return ret+1;
    }
};
struct Union_Find{
    ll N;
    vi par;
    vi siz;
    Union_Find(int n):N(n){
        par.resize(N);
        siz.resize(N,1);
        rep(i,0,N) par[i]=i;
    }
    ll root(ll X){
        if(par[X]==X) return X;
        return par[X]=root(par[X]);
    }
    bool same(ll X,ll Y){
        return root(X)==root(Y);
    }
    void unite(ll X,ll Y){
        X=root(X);
        Y=root(Y);
        if(X==Y) return;
        par[X]=Y;
        siz[Y]+=siz[X];
        siz[X]=0;
    }
    ll size(ll X){
        return siz[root(X)];
    }
};
ll modpow(ll X,ll Y){
    ll sum=X,cnt=1;
    vi A;
    while(cnt<=Y){
        A.pb(sum);
        sum*=sum;
        sum%=MOD;
        cnt*=2;
    }
    int M=A.size();
    ll ret=1;
    REP(i,1,M){
        if(Y>=(1ll<<M-i)){
            Y-=(1ll<<M-i);
            ret*=A[M-i];
            ret%=MOD;
        }
    }
    return ret;
}
ll fac[MAX],finv[MAX],inv[MAX];
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
ll COM(ll n,ll r){
    if(n<r||n<0||r<0) return 0;
    return fac[n]*finv[r]%MOD*finv[n-r]%MOD;
}
signed main(){
    string S; cin>>S;
    if(S.size()==26){
        if(S=="zyxwvutsrqponmlkjihgfedcba"){
            cout<<-1<<endl;
            return 0;
        }
        std::set<char> set;
        set.insert(S[25]);
        per(i,24,0){
            if(*set.rbegin()>S[i]){
                for(auto p:set){
                    if(p>S[i]){
                        S=S.substr(0,i)+p;
                        break;
                    }
                }
                break;
            }
            set.insert(S[i]);
        }
    }
    else{
        vector<bool> F(26,1);
        rep(i,0,S.size()) F[S[i]-'a']=0;
        rep(i,0,26){
            if(F[i]){
                S+=i+'a';
                break;
            }
        }
    }
    cout<<S<<endl;
}
