A non-empty string is called palindrome, if it reads the same from the left to the right and from the right to the left. For example, "abcba", "a", and "abba" are palindromes, while "abab" and "xy" are not.

A string is called a substring of another string, if it can be obtained from that string by dropping some (possibly zero) number of characters from the beginning and from the end of it. For example, "abc", "ab", and "c" are substrings of the string "abc", while "ac" and "d" are not.

Let's define a palindromic count of the string as the number of its substrings that are palindromes. For example, the palindromic count of the string "aaa" is 6 because all its substrings are palindromes, and the palindromic count of the string "abc" is 3 because only its substrings of length 1 are palindromes.

You are given a string s. You can arbitrarily rearrange its characters. You goal is to obtain a string with the maximum possible value of palindromic count.

Input

The first line contains an integer n (1 ≤ n ≤ 100 000) — the length of string s.

The second line contains string s that consists of exactly n lowercase characters of Latin alphabet.

Output

Print string t, which consists of the same set of characters (and each characters appears exactly the same number of times) as string s. Moreover, t should have the maximum possible value of palindromic count among all such strings strings.

If there are multiple such strings, print any of them.

Examples

Input

5
oolol


Output

ololo


Input

16
gagadbcgghhchbdf


Output

abccbaghghghgdfd

Note

In the first example, string "ololo" has 9 palindromic substrings: "o", "l", "o", "l", "o", "olo", "lol", "olo", "ololo". Note, that even though some substrings coincide, they are counted as many times as they appear in the resulting string.

In the second example, the palindromic count of string "abccbaghghghgdfd" is 29.

import java.io.*;
import java.util.Comparator;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;

/**
 * Copyright © 2018 Chris. All rights reserved.
 *
 * @author Chris
 * 2018/7/9 15:33
 * @see format
 */
public class C {

    private static BufferedReader br;
    private static StreamTokenizer st;
    private static PrintWriter pw;

    static final int INF = 1000000007;
    static final int MOD = 1000000007;

    private static void solve() throws IOException {
        int n = nextInt();
        char ch[] = next(n + 10).toCharArray();
        int cnt[] = new int[128];
        for (char c : ch) {
            cnt[c]++;
        }

        StringBuilder ans = new StringBuilder();
        Queue<Character> queue = new PriorityQueue<>(Comparator.comparingInt(o -> -cnt[o]));
        for (int i = 'a'; i <= 'z'; i++) {
            if (cnt[i] > 0) {
                queue.offer((char) i);
            }
        }
        while (!queue.isEmpty()) {
            int tmp = cnt[queue.peek()];
            if (tmp == 1) {
                ans.append(queue.poll());
            } else if (tmp > 1) {
                char fir = queue.poll();
                if (!queue.isEmpty() && tmp == cnt[queue.peek()] + 1) {
                    char sec = queue.poll();
                    ans.append(fir);
                    for (int i = 0; i < cnt[sec]; i++) {
                        ans.append(sec);
                        ans.append(fir);
                    }
                } else {
                    for (int i = 0; i < tmp; i++) {
                        ans.append(fir);
                    }
                }
            }
        }
        pw.print(ans);
    }

    static void getDiv(Map<Integer, Integer> map, int n) {
        int sqrt = (int) Math.sqrt(n);
        for (int i = sqrt; i >= 2; i--) {
            if (n % i == 0) {
                getDiv(map, i);
                getDiv(map, n / i);
                return;
            }
        }
        map.put(n, map.getOrDefault(n, 0) + 1);
    }

    public static boolean[] generatePrime(int n) {
        boolean p[] = new boolean[n + 1];
        p[2] = true;

        for (int i = 3; i <= n; i += 2) {
            p[i] = true;
        }

        for (int i = 3; i <= Math.sqrt(n); i += 2) {
            if (!p[i]) {
                continue;
            }
            for (int j = i * i; j <= n; j += i << 1) {
                p[j] = false;
            }
        }
        return p;
    }

    // 18位素数：154590409516822759
    // 19位素数：2305843009213693951 (梅森素数)
    // 19位素数：4384957924686954497
    static boolean isPrime(long n) { //determines if n is a prime number
        int p[] = {2, 3, 5, 233, 331};
        int pn = p.length;
        long s = 0, t = n - 1;//n - 1 = 2^s * t
        while ((t & 1) == 0) {
            t >>= 1;
            ++s;
        }
        for (int i = 0; i < pn; ++i) {
            if (n == p[i]) {
                return true;
            }
            long pt = pow(p[i], t, n);
            for (int j = 0; j < s; ++j) {
                long cur = llMod(pt, pt, n);
                if (cur == 1 && pt != 1 && pt != n - 1) {
                    return false;
                }
                pt = cur;
            }
            if (pt != 1) {
                return false;
            }
        }
        return true;
    }

    static long llMod(long a, long b, long mod) {
        return (a * b - (long) ((double) a / mod * b + 0.5) * mod + mod) % mod;
//        long r = 0;
//        a %= mod;
//        b %= mod;
//        while (b > 0) {
//            if ((b & 1) == 1) {
//                r = (r + a) % mod;
//            }
//            b >>= 1;
//            a = (a << 1) % mod;
//        }
//        return r;
    }

    static int pow(long a, long n) {
        long ans = 1;
        while (n > 0) {
            if ((n & 1) == 1) {
                ans = (ans * a) % MOD;
            }
            a = (a * a) % MOD;
            n >>= 1;
        }
        return (int) ans;
    }

    static int pow(long a, long n, long mod) {
        long ans = 1;
        while (n > 0) {
            if ((n & 1) == 1) {
                ans = llMod(ans, a, mod);
            }
            a = llMod(a, a, mod);
            n >>= 1;
        }
        return (int) ans;
    }

    private static long[][] initC(int n) {
        long c[][] = new long[n][n];

        for (int i = 0; i < n; i++) {
            c[i][0] = 1;
        }

        for (int i = 1; i < n; i++) {
            for (int j = 1; j <= i; j++) {
                c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
            }
        }
        return c;
    }

    /**
     * ps: n >= m, choose m from n;
     */
    private static int c(long n, long m) {
        if (m > n) {
            n ^= m;
            m ^= n;
            n ^= m;
        }
        m = Math.min(m, n - m);

        long top = 1;
        long bot = 1;
        for (long i = n - m + 1; i <= n; i++) {
            top = (top * i) % MOD;
        }
        for (int i = 1; i <= m; i++) {
            bot = (bot * i) % MOD;
        }

        return (int) ((top * pow(bot, MOD - 2)) % MOD);
    }

    static int gcd(int a, int b) {
        if (a < b) {
            a ^= b;
            b ^= a;
            a ^= b;
        }
        while (b != 0) {
            int tmp = a % b;
            a = b;
            b = tmp;
        }
        return a;
    }

    static boolean even(long n) {
        return (n & 1) == 0;
    }

    public static void main(String args[]) throws IOException {
        boolean oj = System.getProperty("ONLINE_JUDGE") != null;
        if (!oj) {
            System.setIn(new FileInputStream("in.txt"));
//            System.setOut(new PrintStream("out.txt"));
        }
        br = new BufferedReader(new InputStreamReader(System.in));
        st = new StreamTokenizer(br);
        pw = new PrintWriter(new OutputStreamWriter(System.out));
        st.ordinaryChar('\''); //指定单引号、双引号和注释符号是普通字符
        st.ordinaryChar('\"');
        st.ordinaryChar('/');

        long t = System.currentTimeMillis();
        solve();
        if (!oj) {
            pw.println("[" + (System.currentTimeMillis() - t) + "ms]");
        }
        pw.flush();
    }

    private static long[] anLong(int n) throws IOException {
        long a[] = new long[n];
        for (int i = 0; i < n; i++) {
            a[i] = nextInt();
        }
        return a;
    }

    private static String next(int len) throws IOException {
        char ch[] = new char[len];
        int cur = 0;
        char c;
        while ((c = (char) br.read()) == '\n' || c == '\r' || c == ' ' || c == '\t') ;
        do {
            ch[cur++] = c;
        } while (!((c = (char) br.read()) == '\n' || c == '\r' || c == ' ' || c == '\t'));
        return String.valueOf(ch, 0, cur);
    }

    private static int nextInt() throws IOException {
        st.nextToken();
        return (int) st.nval;
    }

    private static long nextLong() throws IOException {
        return Long.parseLong(nextLine());
    }

    private static double nextDouble() throws IOException {
        st.nextToken();
        return st.nval;
    }

    private static String[] nextSS(String reg) throws IOException {
        return br.readLine().split(reg);
    }

    private static String nextLine() throws IOException {
        return br.readLine();
    }
}
