#include <bits/stdc++.h>
using namespace std;
template <class c>
struct rge {
  c b, e;
};
template <class c>
rge<c> range(c i, c j) {
  return rge<c>{i, j};
}
template <class c>
auto dud(c* x) -> decltype(cerr << *x, 0);
template <class c>
char dud(...);
struct debug {
  ~debug() { cerr << endl; }
  template <class c>
  typename enable_if<sizeof dud<c>(0) != 1, debug&>::type operator<<(c i) {
    cerr << boolalpha << i;
    return *this;
  }
  template <class c>
  typename enable_if<sizeof dud<c>(0) == 1, debug&>::type operator<<(c i) {
    return *this << range(begin(i), end(i));
  }
  template <class c, class b>
  debug& operator<<(pair<b, c> d) {
    return *this << "(" << d.first << ", " << d.second << ")";
  }
  template <class c>
  debug& operator<<(rge<c> d) {
    *this << "[";
    for (auto it = d.b; it != d.e; ++it) *this << ", " + 2 * (it == d.b) << *it;
    return *this << "]";
  }
};
long double eps = (long double)1 / 1e6;
const long double pi = 3.14159265359;
long long inf = 1e18, mod1 = 1e9 + 7;
long long sqr(long long a) { return a * a; }
long long qb(long long a) { return a * a * a; }
template <typename T>
bool umax(T& a, T b) {
  return a < b ? a = b, 1 : 0;
}
template <typename T>
bool umin(T& a, T b) {
  return b < a ? a = b, 1 : 0;
}
bool is_prime(long long val) {
  for (long long i = 2; i <= sqrt(val); i++)
    if (val % i == 0) return 0;
  return 1;
}
long long gcd(long long a, long long b) { return !a ? b : gcd(b % a, a); }
long long binpow(long long a, long long b, long long mod) {
  return b ? (b % 2 ? (a * (sqr(binpow(a, b / 2, mod)) % mod)) % mod
                    : sqr(binpow(a, b / 2, mod)) % mod)
           : 1;
}
long long binmult(long long a, long long b, long long mod) {
  return b ? (b % 2 ? (2 * binmult(a, b / 2, mod) + a) % mod
                    : (2 * binmult(a, b / 2, mod)) % mod)
           : 0;
}
const long long RR = 1e4;
const long long tx[8] = {1, -1, 2, -2, -1, -2};
const long long ty[8] = {-2, -2, -1, -1, 2, 1};
const char rev_to[4] = {'E', 'W', 'N', 'S'};
const int N = 5e3 + 1;
const int ppp = 73;
const int pr = 3;
const int block = 600;
const int OPEN = 0;
const int CLOSE = 1;
auto rnd = bind(uniform_int_distribution<int>(1, 5969699), mt19937(time(0)));
void bad() {
  cout << "IMPOSSIBLE";
  exit(0);
}
int dp[N][26][26];
pair<int, int> p[N][26][26];
signed main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(0);
  ;
  int n, m;
  cin >> n >> m;
  vector<string> a(n);
  for (auto& z : a) cin >> z;
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j < 26; j++) {
      for (int t = 0; t < 26; t++) dp[i][j][t] = 2e9;
    }
  }
  for (int i = 0; i < n; i++) {
    for (int c1 = 0; c1 < 26; c1++) {
      for (int c2 = 0; c2 < 26; c2++) {
        if (c1 == c2) continue;
        for (int j = 0; j < m; j++) {
          int t = (j % 2 ? (a[i][j] - 'a' != c2) : (a[i][j] - 'a' != c1));
          dp[i][c1][c2] += t;
        }
        for (int o1 = 0; o1 < 26; o1++) {
          for (int o2 = 0; o2 < 26; o2++) {
            if (o1 == c1 || o2 == c2) continue;
            if (o1 == o2) continue;
            if (umin(dp[i + 1][o1][o2], dp[i][c1][c2])) {
              p[i + 1][o1][o2] = {c1, c2};
            }
          }
        }
      }
    }
  }
  pair<int, int> c;
  int a1 = 2e9;
  int lvl = n;
  for (int c1 = 0; c1 < 26; c1++) {
    for (int c2 = 0; c2 < 26; c2++) {
      if (c1 == c2) continue;
      if (umin(a1, dp[n - 1][c1][c2])) c = {c1, c2};
    }
  }
  while (lvl--) {
    for (int j = 0; j < m; j++) {
      if (j % 2 == 0)
        a[lvl][j] = char(c.first + 'a');
      else
        a[lvl][j] = char(c.second + 'a');
    }
    c = p[lvl][c.first][c.second];
  }
  cout << a1 << "\n";
  for (auto& z : a) cout << z << "\n";
  return 0;
}
