#include <bits/stdc++.h>
using namespace std;
int r, c, visited[24][24], ret = 1, cnt[26];
int dy[] = {-1, 0, 1, 0};
int dx[] = {0, 1, 0, -1};
char a[24][24];
 
int dfs(int y, int x){
    int ret = 1;
    for(int i = 0; i < 4; i++){
        int ny = y + dy[i];
        int nx = x + dx[i];
        if(ny < 0 || ny >= r || nx < 0 || nx >= c || visited[ny][nx] || cnt[a[ny][nx] - 'A']) continue;
        visited[ny][nx] = 1;
        cnt[a[ny][nx] - 'A'] = 1;
        ret += dfs(ny, nx);
    }
    return ret;
}
int main(){
    cin >> r >> c;
    for(int i = 0; i < r; i++){
        for(int j = 0; j < c; j++){
            cin >> a[i][j];
        }
    }
 
    visited[0][0] = 1;
    cnt[a[0][0] - 'A'] = 1;
    cout << dfs(0, 0) << '\n';
}

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MyAzCkFCQQpCQUEKQ0FB

3 3
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CAA