#include <iostream>
#include <algorithm>

using namespace std;
int main() {
    int n;
    cin >> n;
    string s;
    cin >> s;
    int minIdx;
    for (int i = 0; i < n; i++) {
        minIdx = i;
        for (int j = i + 1; j < n; j++)
            if (s[minIdx] > s[j]) minIdx = j;
        swap(s[i], s[minIdx]);
    }
    cout << s;

    return 0;
}