# include <bits/stdc++.h>
using namespace std;
#define ll long long
signed main(){
    
    string s; cin>>s;
    vector<ll>freq(26);
    for(auto it:s) freq[it-'a']++;
    bool f=0;
    for(ll i=0;i<26;i++)
    {
      if(freq[i]!=0) {cout<<char(i+'a'); f=1;}
      if(f) break;
    }
    if(!f) cout<<-1<<endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
#define int long long

int solve(int n, vector<int>& front, vector<int>& back, int frontend, int backend) {
    vector<vector<int>> dp(n + 1, vector<int>(frontend + 1, INT_MAX));
    dp[0][0] = 0;

    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= frontend; j++) {
            if (dp[i][j] == INT_MAX) continue;
            if (j < frontend) {
                dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j] + front[i]);
            }
            int b = i - j;
            if (b < backend) {
                dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + back[i]);
            }
        }
    }

    return dp[n][frontend];
}

int32_t main() {
    int frontend, backend;
    cin >> frontend >> backend;
    int n = frontend + backend;
    vector<int> front(n), back(n);
    
    for (int i = 0; i < n; i++) {
        cin >> front[i];
    }
    for (int i = 0; i < n; i++) {
        cin >> back[i];
    }

    int result = solve(n, front, back, frontend, backend);
    cout << result << endl;

    return 0;
}

#include <bits/stdc++.h>
#define ll long long
using namespace std;

ll ss(ll A, ll B) {
    ll rounds = 0;
        while (A != B) {
        if (A > B) {
            A -= B;
        } else {
            B -= A;
        }
        rounds++; 
    }
    
    return rounds;
}

int main() {
    ll A, B;
    cin >> A >> B;
    cout << ss(A, B) << endl;
    return 0;
}

#include <bits/stdc++.h>
#define MOD 1000000007
using namespace std;

int solve(int n, int m, int x, vector<int>& a) {

    int rem = m % x;

    if (rem == 0) {
        return m % MOD;
    }

    int minAdd = -1;
    for (int i = 0; i < n; i++) {
        int add = a[i];
        if ((m + add) % x == 0) {
            if (minAdd == -1 || add < minAdd) {
                minAdd = add;
            }
        }
    }

    if (minAdd == -1) {
        return -1;
    }

    return (m + minAdd) % MOD;
}

int main() {
    int t; 
    cin >> t;
    
    while (t--) {
        int n, m, x;
        cin >> n >> m >> x;
        
        vector<int> a(n);
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }

        int res =solve(n, m, x, a);

        cout << res << endl;
    }

    return 0;
}

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
int32_t main(){
    ll n,m;
    cin>>n>>m;
    vector<ll> a(n);
    vector<ll> b(m);
    vector<ll> pre(n+1);
    for(int i=0;i<n;i++){
        cin>>a[i];
        pre[i+1]=pre[i]+a[i];
    }
    for(int i=0;i<m;i++){
        cin>>b[i];
    }
    ll k=(1LL<<m)-1;
    ll dp[n+1][k+1];
    for(int i=0;i<=n;i++){
        for(int j=0;j<=k;j++){
            dp[i][j]=0;
        }
    }
    for(int i=1;i<=n;i++){
        for(int j=0;j<=k;j++){
            dp[i][j]=max(dp[i][j],dp[i-1][j]);
            for(int l=0;l<m;l++){
                if((1LL<<l)&j){
                
                }
                else{
                    ll next=(1LL<<l)|j,idx=i+b[l]-1;
                    if(idx>=0 and idx<=n)
                    dp[idx][next]=max(dp[idx][next],dp[i-1][j]+pre[idx]-pre[i-1]);
                }
            }
        }
    }
    ll ans=0;
    for(int i=0;i<=n;i++){
        ans=max(dp[i][k],ans);
    }
    cout<<ans<<endl;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
#define ll long long
vector<ll> msk(1024,-1);
void digits(ll num1) {
    string str1 = to_string(num1);
    set<ll>s;
    for (char digit : str1) {
        ll d=digit-'0';
        s.insert(d);
    }
    ll val=0;
    for(auto it:s) val+=(1<<it);
    msk[val]=max(msk[val],num1);
}

ll solution(vector<ll>& A) {
    for(auto &it:msk) it=-1; 
    ll ans=-1;
    for(auto it:A) digits(it);
    for(ll i=1;i<1024;i++){
        if(msk[i]==-1) continue;
        for(ll j=i+1;j<1024;j++){
            if(msk[j]==-1) continue;
            ll fl=0;
            for(ll k=0;k<10;k++){
                if((1<<k)&i){
                    if((1<<k)&j){
                        fl=1;
                        continue;
                    }
                }
            }
            if(fl) continue;
            ans=max(ans,msk[i]+msk[j]);
        }
    }
    return ans;
}