#include <bits/stdc++.h>
using namespace std;
string makeLexicographicallySmallestPalindrome(string s) {
    int n = s.length();
    unordered_map<char, int> a;
    string b;
    for (char c : s) {
        a[c]++;
    }
    for (char c = 'a'; c <= 'z'; c++) {
        if (a[c] % 2 != 0) {
            b += c;
        }
    }
    int m = b.length();
    int p = 0;
    for (int i = m - 1; i >= m / 2; i--) {
        char x = b[i];
        char y = b[p];
        a[x]--;
        b[i] = y;
        a[y]++;
        p++;
    }

    string c, d, e;
    for (char c1 = 'a'; c1 <= 'z'; c1++) {
        int f = a[c1];
        if (f != 0) {
            if (f % 2 == 0) {
                c += string(f / 2, c1);
            } else {
                c += string((f - 1) / 2, c1);
                d += c1;
            }
        }
    }
    e = c;
    reverse(e.begin(), e.end());
    return c + d + e;
}
int main() {
    string s;
    cin >> s;
    cout <<makeLexicographicallySmallestPalindrome(s) << endl;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
string all_happy(int a, int b, vector<int> c) {
    vector<int> d = c; 
    sort(d.begin(), d.end()); 
    
    int e = 0; 
    vector<int> f(a + 1, 0); 
    
    auto g = [&](int h, int i) { 
        for (; h <= a; h += h & -h) { 
            f[h] += i; 
        } 
    }; 
    
    auto j = [&](int h) { 
        int k = 0; 
        for (; h > 0; h -= h & -h) { 
            k += f[h]; 
        } 
        return k; 
    }; 

    for (int l = 0; l < a; ++l) { 
        int m = lower_bound(d.begin(), d.end(), c[l]) - d.begin() + 1; 
        e += j(a) - j(m); 
        g(m, 1); 
    } 

    if (e == 0) return "YES"; 
    
    if (b == 0 || e % b != 0) return "NO"; 
    
    
    return e / b > 0 ? "YES" : "NO"; 
}

#include <bits/stdc++.h>
using namespace std;
void bfs(int a, vector<vector<int>>& b, vector<bool>& c) {
    queue<int> d;
    d.push(a);
    c[a] = true;
    while (!d.empty()) {
    int e = d.front();
    d.pop();
    for (int f = 0; f < b.size(); ++f) {
    if (b[e][f] == 1 && !c[f]) {
    c[f] = true;
    d.push(f);
            }
        }
    }
}
int solve(int a, int b, vector<vector<int>>& c, vector<int>& d) {
    int e = INT_MAX, f = -1;
    for (int g : d) {
    vector<bool> h(a, false);
    vector<vector<int>> i = c;
    for (int j = 0; j < a; ++j) {
    i[g][j] = 0;
    i[j][g] = 0;
    }
    int k = 0;
    for (int l : d) 
    {
    if (!h[l]) {
    bfs(l, i, h);
    }
    }
    k = count(h.begin(), h.end(), true);
    if (k < e || (k == e && g < f)) 
    {
    e = k;
    f = g;
    }
    }
    return f;
}

int main() {
    int a, b;
    cin >> a >> b;
    vector<vector<int>> c(a, vector<int>(a));
    for (int d = 0; d < a; ++d) {
    for (int e = 0; e < a; ++e) 
    {
            cin >> c[d][e];
    }
    }
    vector<int> d(b);
    for (int e = 0; e < b; ++e) 
    {
    cin >> d[e];
    }
    cout << solve(a, b, c, d) << endl;
    return 0;
}

class CommunicationException(Exception):
    def __init__(self, message):
        super().__init__(message)

class Caller:
    def __init__(self, name):
        self.name = name

class CommsHandlerABC:
    def connect(self, user1, user2):
        pass

    def hangup(self, user1, user2):
        pass

    def clear_all(self):
        pass

class CommsHandler(CommsHandlerABC):
    def __init__(self, users):
        self.connected_users = set()
        self.user_objects = [Caller(user) for user in users]

    def connect(self, user1_idx, user2_idx) -> str:
        user1 = self.user_objects[user1_idx]
        user2 = self.user_objects[user2_idx]

        if user1.name == user2.name:
            raise CommunicationException(f"{user1.name} cannot connect with {user2.name}")

        if self.is_line_in_use():
            raise CommunicationException("Connection in use. Please try later")

        connection = frozenset([user1.name, user2.name]) 
        if connection in self.connected_users:
            raise CommunicationException(f"Connection between {user1.name} and {user2.name} already exists")

        self.connected_users.add(connection)
        return f"Success: Connection established between {user1.name} and {user2.name} "

    def hangup(self, user1_idx, user2_idx) -> str:
        user1 = self.user_objects[user1_idx]
        user2 = self.user_objects[user2_idx]

        if user1.name == user2.name:
            raise CommunicationException(f"{user1.name} cannot hangup with {user2.name}")

        connection = frozenset([user1.name, user2.name])  
        if connection in self.connected_users:
            self.connected_users.remove(connection)
            return f"Success: {user1.name} and {user2.name} are disconnected "
        else:
            raise CommunicationException(f"{user1.name} and {user2.name} not found in the communication channel")

    def clear_all(self):
        self.connected_users.clear()

    def is_line_in_use(self) -> bool:
        return len(self.connected_users) >= 2