#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const string str = "ATGC";
vector<string> s, tmp, ans;
int main() {
  ios::sync_with_stdio(0);
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < n; i++) {
    string st;
    cin >> st;
    s.push_back(st);
  }
  int ansmin = INF, now;
  for (int c1 = 0; c1 < 4; c1++)
    for (int c2 = c1 + 1; c2 < 4; c2++) {
      string t;
      set<int> st;
      for (int i = 0; i < 4; i++) st.insert(i);
      st.erase(c1);
      st.erase(c2);
      set<int>::iterator it = st.begin();
      t.push_back(str[c1]);
      t.push_back(str[c2]);
      t.push_back(str[*(it++)]);
      t.push_back(str[*it]);
      now = 0;
      tmp.clear();
      for (int i = 0; i < n; i++) {
        tmp.push_back("");
        int b = (i & 1) << 1;
        int cnt1 = 0, cnt2 = 0;
        for (int j = 0; j < m; j++) {
          if (s[i][j] != t[b + (j & 1)]) ++cnt1;
          if (s[i][j] != t[b + ((j & 1) ^ 1)]) ++cnt2;
        }
        if (cnt1 < cnt2)
          for (int j = 0; j < m; j++) tmp[i].push_back(t[b + (j & 1)]);
        else
          for (int j = 0; j < m; j++) tmp[i].push_back(t[b + ((j & 1) ^ 1)]);
        now += min(cnt1, cnt2);
      }
      if (now < ansmin) {
        ans = tmp;
        ansmin = now;
      }
      now = 0;
      tmp.clear();
      for (int i = 0; i < n; i++) tmp.push_back("");
      for (int j = 0; j < m; j++) {
        int b = (j & 1) << 1;
        int cnt1 = 0, cnt2 = 0;
        for (int i = 0; i < n; i++) {
          if (s[i][j] != t[b + (i & 1)]) ++cnt1;
          if (s[i][j] != t[b + ((i & 1) ^ 1)]) ++cnt2;
        }
        if (cnt1 < cnt2)
          for (int i = 0; i < n; i++) tmp[i].push_back(t[b + (i & 1)]);
        else
          for (int i = 0; i < n; i++) tmp[i].push_back(t[b + ((i & 1) ^ 1)]);
        now += min(cnt1, cnt2);
      }
      if (now < ansmin) {
        ans = tmp;
        ansmin = now;
      }
    }
  for (int i = 0; i < n; i++) cout << ans[i] << endl;
  return 0;
}
