#include <bits/stdc++.h>
void read(int &x) {
  x = 0;
  int flag = 1;
  char ch = ' ';
  while (ch < '0' || ch > '9') {
    if (ch == '-') flag = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  x *= flag;
}
void read(long long &x) {
  x = 0;
  int flag = 1;
  char ch = ' ';
  while (ch < '0' || ch > '9') {
    if (ch == '-') flag = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  x *= flag;
}
using namespace std;
const int dx[4][5] = {
    {0, 1, 2, 2, 2}, {0, 1, 1, 1, 2}, {0, 0, 0, 1, 2}, {0, 1, 1, 1, 2}};
const int dy[4][5] = {
    {1, 1, 0, 1, 2}, {0, 0, 1, 2, 0}, {0, 1, 2, 1, 1}, {2, 0, 1, 2, 2}};
int n, m, best, rest;
char ans[10][10], now[10][10];
bool vis[10][10];
void dfs(int cur, int x, int y) {
  if (x + 2 > n) {
    if (cur > best) {
      best = cur;
      for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++) ans[i][j] = now[i][j];
    }
    return;
  }
  if (y + 2 > m) {
    dfs(cur, x + 1, 1);
    return;
  }
  if (rest / 5 + cur <= best) return;
  rest -= now[x][y] == '.';
  for (int i = 0; i <= 3; i++) {
    bool flag = 1;
    for (int j = 0; j <= 4; j++)
      if (vis[x + dx[i][j]][y + dy[i][j]]) flag = 0;
    if (!flag) continue;
    rest -= 5;
    for (int j = 0; j <= 4; j++)
      vis[x + dx[i][j]][y + dy[i][j]] = 1,
                            now[x + dx[i][j]][y + dy[i][j]] = cur + 'A';
    dfs(cur + 1, x, y + 1);
    for (int j = 0; j <= 4; j++)
      vis[x + dx[i][j]][y + dy[i][j]] = 0,
                            now[x + dx[i][j]][y + dy[i][j]] = '.';
    rest += 5;
  }
  dfs(cur, x, y + 1);
  rest += now[x][y] == '.';
}
int main() {
  read(n), read(m);
  if (n < 3 || m < 3) {
    puts("0");
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) putchar('.');
      puts("");
    }
    return 0;
  }
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) ans[i][j] = now[i][j] = '.';
  rest = n * m;
  dfs(0, 1, 1);
  printf("%d\n", best);
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) putchar(ans[i][j]);
    puts("");
  }
  return 0;
}
