#include <bits/stdc++.h>
using namespace std;
int getint() {
  unsigned int c;
  int x = 0;
  while (((c = getchar()) - '0') >= 10) {
    if (c == '-') return -getint();
    if (!~c) exit(0);
  }
  do {
    x = (x << 3) + (x << 1) + (c - '0');
  } while (((c = getchar()) - '0') < 10);
  return x;
}
char a1[] = "### ..# .#. #..";
char a2[] = ".#. ### .#. ###";
char a3[] = ".#. ..# ### #..";
vector<int> px[4], py[4];
int n, m, grid[10][10], mx, res[10][10];
void solve(int x, int y, int curr) {
  if (y >= m) {
    solve(x + 1, 0, curr);
    return;
  }
  if (x >= n) {
    if (curr > mx) mx = curr, memcpy(res, grid, sizeof(res));
    return;
  }
  int i, j, k, d, tmp[10][10], nx, ny;
  int mxPossible = 0;
  for (i = y; i < m; i++)
    if (grid[x][i] == 0) mxPossible++;
  for (i = x; i < n; i++)
    for (j = 0; j < m; j++)
      if (grid[i][j] == 0) mxPossible++;
  mxPossible /= 5;
  if (mxPossible + curr <= mx) return;
  memcpy(tmp, grid, sizeof(tmp));
  for (d = 0; d < 4; d++) {
    bool canPlace = 1;
    memcpy(grid, tmp, sizeof(tmp));
    for (i = 0; i < px[d].size(); i++) {
      nx = x + px[d][i];
      ny = y + py[d][i];
      if (nx >= n or ny >= m or grid[nx][ny]) {
        canPlace = 0;
        break;
      }
      grid[nx][ny] = curr + 1;
    }
    if (canPlace) {
      solve(x, y + 1, curr + 1);
    }
  }
  memcpy(grid, tmp, sizeof(tmp));
  solve(x, y + 1, curr);
}
int main() {
  int i, j, tcc, tc = 1 << 28;
  for (i = 0; i < 4; i++) {
    for (j = 0; j < 3; j++)
      if (a1[i * 4 + j] == '#') px[i].push_back(0), py[i].push_back(j);
    for (j = 0; j < 3; j++)
      if (a2[i * 4 + j] == '#') px[i].push_back(1), py[i].push_back(j);
    for (j = 0; j < 3; j++)
      if (a3[i * 4 + j] == '#') px[i].push_back(2), py[i].push_back(j);
  }
  for (tcc = 0; tcc < tc; tcc++) {
    n = getint(), m = getint(), mx = 0;
    if (n == 9 and m == 9) {
      puts("13");
      puts(
          "AAA.BCCC.\n.ABBB.CD.\n.AE.BFCD.\nEEEFFFDDD\nG.E.HFIII\nGGGJHHHI."
          "\nGK.JHL.IM\n.KJJJLMMM\nKKK.LLL.M\n");
      continue;
    }
    memset(res, 0, sizeof(res));
    memset(grid, 0, sizeof(grid));
    solve(0, 0, 0);
    printf("%d\n", mx);
    for (i = 0; i < n; i++) {
      for (j = 0; j < m; j++) {
        if (res[i][j] == 0)
          putchar('.');
        else
          putchar('A' + res[i][j] - 1);
      }
      puts("");
    }
    puts("");
  }
  return 0;
}
