#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    vector<string> s(n);
    rep(i, n) cin >> s[i];
    rep(_, 2) {
        int x = s.size();
        int y = s[0].size();
        vector<string> t(y);
        rep(i, x) rep(j, y) {
            t[j].push_back(s[i][j]);
        }
        s = t;
        for (auto &v : s)
            sort(v.begin(), v.end());
    }
    for (auto t : s)
        cout << t << endl;
    return 0;
}