#include <iostream>
#include <vector>
#include <cstring>
using namespace std;
#define MAX 1000010
vector <char> c[MAX];
char x[MAX];
int ptr[MAX], valid, fr[30];
int main()
{
    int n, i, j, ok;
    n = 0;
    while(cin)
    {
        cin >> x;
        c[n].resize(strlen(x));
        for(i = 0 ; x[i] ; i++)
        {
            c[n][i] = x[i];
           // cout << x[i];
        }
        n++;
    }
    n--;
    for(i = 0 ; i <= n ; i++)
    {
        ptr[i] = 0;
    }
    valid = n + 1;
    while(valid)
    {
        for(i = 0 ; i < 26 ; i++)
            fr[i] = 0;
        for(i = 0 ; i <= n ; i++)
        {
            if(ptr[i] < c[i].size())
                fr[c[i][ptr[i]] - 'a']++;
        }
        ok = 0;
        for(i = 0 ; i < 26 ; i++)
        {
            if(fr[i] > fr[ok])
                ok = i;
        }
        cout << (char)(ok + 'a');
        for(i = 0 ; i <= n ; i++)
        {
            if(ptr[i] < c[i].size())
                if(c[i][ptr[i]] - 'a' == ok)
                {
                    ptr[i]++;
                    if(ptr[i] == c[i].size())
                        valid--;
                }
        }
    }
}