#include<bits/stdc++.h>
#include<atcoder/all>
#define chmin(x,y) (x) = min((x),(y))
#define chmax(x,y) (x) = max((x),(y))
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define vec vector
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back 
#define eb emplace_back

using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
const ll mod = 998244353;
using mint = modint998244353;
const vector<int> dx = {1,0,-1,0}, dy = {0,1,0,-1};
// using Graph = vector<vector<pair<int,ll>>>;
using Graph = vector<vector<int>>;

int main(){
  // input + prep
  int N,M;
  cin >> N >> M;
  vector<string> S(N), sort1(M);
  rep(i,N){
    cin >> S[i];
    rep(j,M) sort1[j] += S[i][j];
  }
  
  // solve
  vector<string> sort2(N);
  rep(j,M){
    sort(all(sort1[j]));
    assert(sort1[j].size() == N);
    rep(i,N) sort2[i] += sort1[j][i];
  }
  
  // output
  rep(i,N){
    sort(all(sort2[i]));
    cout << sort2[i] << endl;
  }
}