#include <bits/stdc++.h>
using namespace std;
const int moves[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}}};
int n, m;
char grid[10][10];
char sol[10][10];
char maxL;
void dfs(int x, int y, char L) {
  if (L + (n - x) * (m - y) / 2 < maxL) {
    return;
  }
  if (y + 2 >= m) {
    dfs(x + 1, 0, L);
    return;
  }
  if (x + 2 >= n) {
    if (L > maxL) {
      for (int i = 0; i < n; i++) {
        strcpy(sol[i], grid[i]);
      }
      maxL = L;
    }
    return;
  }
  for (int i = 0; i < 4; i++) {
    int j;
    for (j = 0; j < 5; j++) {
      if (grid[x + moves[i][j][0]][y + moves[i][j][1]] != '.') break;
    }
    if (j == 5) {
      for (j = 0; j < 5; j++) {
        grid[x + moves[i][j][0]][y + moves[i][j][1]] = L;
      }
      dfs(x, y + 1, L + 1);
      for (j = 0; j < 5; j++) {
        grid[x + moves[i][j][0]][y + moves[i][j][1]] = '.';
      }
    }
  }
  dfs(x, y + 1, L);
}
int main(void) {
  scanf("%d %d", &n, &m);
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      sol[i][j] = grid[i][j] = '.';
    }
  }
  if (n < 3 || m < 3) {
    printf("0\n");
    for (int i = 0; i < n; i++) {
      printf("%s\n", sol[i]);
    }
  } else {
    dfs(0, 0, 'A');
    printf("%d\n", maxL - 'A');
    for (int i = 0; i < n; i++) {
      printf("%s\n", sol[i]);
    }
  }
  return 0;
}
