//排列字符串
#include<iostream>
#include<string>
#include<vector>
using namespace std;
bool comp1(string s1,string s2)
{
    if(s1.size()>s2.size()) return 1;
    else if(s1.size()<s2.size()) return 0;
    else {
        for(int i=0;i<s1.size();i++)
        {
            if(s1[i]>s2[i]) return 1;
            else if(s1[i]<s2[i]) return 0; 
        }
    }
    return 1;
}
bool comp2(string s1,string s2)
{
    if(s1.size()>s2.size()) return 1;
    else if(s1.size()<s2.size()) return 0;
    else {
        for(int i=0;i<s1.size();i++)
        {
            if(s1[i]>s2[i]) return 1;
            else if(s1[i]<s2[i]) return 0; 
        }
    }
    return 0;
}
bool issym(string s1)
{
    for(int i=0,j=s1.size()-1;i<j;i++,j--)
    {
        if(s1[i]!=s1[j]) return 0;
    }
    return 1;
}

void ssort(vector<string> &s1,int l,int r)
{
    if(l>=r) return ;
    int i=l,j=r;
    string pivot=s1[i];
    while(i<j)
    {
        while(comp1(s1[j],pivot)&&i<j) j--;
        if(i<j) s1[i]=s1[j];
        while(comp2(pivot,s1[i])&&i<j) i++;
        if(i<j) s1[j]=s1[i];
    }
    s1[i]=pivot;
    ssort(s1,l,i-1);
    ssort(s1,i+1,r);
}

int main()
{
    vector<string> s;
    string s1;
    getline(cin,s1);
    while(s1!="0")
    {
        if(issym(s1)) s.push_back(s1);
        getline(cin,s1);
    }
    ssort(s,0,s.size()-1);
    for(int i=0;i<s.size();i++)
        cout<<s[i]<<endl;

}