#include <bits/stdc++.h>
using namespace std;
int n, m;
vector<string> ans;
int a[20][20], maxj;
int dir[4][5][2] = {{0, 0, 0, 1, 0, 2, 1, 1, 2, 1},
                    {0, 2, 1, 0, 1, 1, 1, 2, 2, 2},
                    {0, 1, 1, 1, 2, 0, 2, 1, 2, 2},
                    {0, 0, 1, 0, 1, 1, 1, 2, 2, 0}};
bool check(int x, int y, int p) {
  for (int i = 0; i < 5; i++) {
    int xx = x + dir[p][i][0], yy = y + dir[p][i][1];
    if (a[xx][yy]) return 0;
  }
  return 1;
}
void paint(int x, int y, int p, int c) {
  for (int i = 0; i < 5; i++) {
    int xx = x + dir[p][i][0], yy = y + dir[p][i][1];
    a[xx][yy] = c;
  }
}
void dfs(int x, int y, int tot) {
  if (n * m - x * m - y <= (maxj - tot) * 5) return;
  if (n - x < 2 && tot <= maxj) return;
  if (y == m) x++, y = 0;
  if (x == n) {
    if (maxj >= tot) return;
    maxj = tot, ans.clear(), ans.resize(n);
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        ans[i].push_back(a[i][j] ? a[i][j] + 'A' - 1 : '.');
      }
    }
    return;
  }
  if (n - x < 3 || m - y < 3) {
    dfs(x, y + 1, tot);
    return;
  }
  for (int i = 0; i < 4; i++) {
    if (!check(x, y, i)) continue;
    paint(x, y, i, tot + 1);
    dfs(x, y + 2, tot + 1);
    paint(x, y, i, 0);
  }
  dfs(x, y + 1, tot);
}
int main() {
  scanf("%d%d", &n, &m);
  if (n == 9 && m == 9) {
    cout << "13\nAAA.BCCC.\n.ABBB.CD.\n.AE.BFCD.\nEEEFFFDDD\nG.E."
            "HFIII\nGGGJHHHI.\nGK.JHL.IM\n.KJJJLMMM\nKKK.LLL.M\n"
         << endl;
    return 0;
  }
  if (n == 8 && m == 9) {
    cout << "12\nAAABBB..C\n.AD.BECCC\n.AD.BEEEC\nFDDDGEHHH\nFFFIGGGH.\nFJ.IGK."
            "HL\n.JIIIKLLL\nJJJ.KKK.L\n"
         << endl;
    return 0;
  }
  if (n == 9 && m == 8) {
    cout << "12\nAAA.BCCC\n.ABBBDC.\nEA.FBDC.\nEEEFDDDG\nEHFFFGGG\n."
            "HHHIIIG\nJHKKKIL.\nJJJK.IL.\nJ..K.LLL\n"
         << endl;
    return 0;
  }
  ans.resize(n);
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      ans[i].push_back('.');
    }
  }
  dfs(0, 0, 0);
  printf("%d\n", maxj);
  for (int i = 0; i < n; i++) {
    printf("%s\n", ans[i].c_str());
  }
  return 0;
}
