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

typedef long long ll;
typedef long double ld;
typedef vector<int> vint;

#define endl "\n"
#define all(x) x.begin(),x.end()
#define allr(x) x.rbegin(),x.rend()
#define oi ostream_iterator
#define write(x,type,method) copy(x.begin(), x.end(), oi<type>(method, " "))
#define writeln(x,type,method) copy(x.begin(), x.end(), oi<type>(method, " ")); method << endl;
#define xfor(name,x1,x2) for(ll name = x1; name <= x2; name++)
#define refor(name,x1,x2) for(ll name = x1; name >= x2; name--)



int main()
{
    ios_base::sync_with_stdio(false);
    ifstream cin("input.txt");

    const string smb = "qwertyuiopasdfghjklzxcvbnm_1234567890";

    string s;
    cin >> s;

    string mn = s;
    xfor(i, 0, smb.size() - 1)
    {
        char del = smb[i];
        string dbl = s;

        bool f = false;
        refor(j, s.size() - 1, 0)
        {
            if(dbl[j] == del)
            {
                erase(v.dw);
            }
        }

        if(f)
        {
            if(dbl < mn) mn = dbl;
        }
    }

    cout << mn;

    return 0;
}