#include <iostream>
#include <queue>
#include <deque>
#include <vector>
#include <cstring>
#include <functional>
using namespace std;
//'.' R G B P Y
char arr[12][6];
int chk[12][6];

const int dx[] = { 0,1,0,-1 };
const int dy[] = { 1,0,-1,0 };

//아래에 .이 있다면 밑으로 내려주자
void gravity() {
    for (int i = 0; i < 6; i++) {
        int p = -1;
        int q = 11;
        while (q >= 0) {
            if (p==-1 && arr[q][i] == '.') {
                p = q;
            }
            else if (p!=-1 && arr[q][i] != '.') {
                arr[p][i] = arr[q][i];
                arr[q][i] = '.';
                q = p;
                p = -1;
            }
            q--;
        }
    }
}

//4개이상 연결되어있으면 .으로 바꿔주자
bool bfs() {
    memset(chk, 0, sizeof(chk));
    vector<pair<int, int>> eraseList;
    bool result = true;
    for (int i = 0; i < 12; i++) {
        for (int j = 0; j < 6; j++) {
            if (arr[i][j] != '.' && chk[i][j] == 0) {
                char color = arr[i][j];
                chk[i][j] = 1;
                queue<pair<int, int>> q;
                vector<pair<int, int>> v;
                q.push({i,j});
                v.push_back({ i,j });
                while (!q.empty()) {
                    int x = q.front().first;
                    int y = q.front().second;
                    q.pop();
                    for (int dir = 0; dir < 4; dir++) {
                        int nx = x + dx[dir];
                        int ny = y + dy[dir];
                        if (nx >= 0 && nx < 12 && ny >= 0 && ny < 6) {
                            if (chk[nx][ny] == 0 && arr[nx][ny] == color) {
                                q.push({nx,ny});
                                v.push_back({nx,ny});
                                chk[nx][ny] = 1;
                            }
                        }
                    }
                }
                if (v.size() >= 4) {
                    for (auto x : v) {
                        eraseList.push_back(x);
                    }
                    result = false;
                }
            }
        }
    }
    for (auto x : eraseList) {
        arr[x.first][x.second] = '.';
    }
    //1개라도 터지면 false리턴
    return result;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    
    for (int i = 0; i < 12; i++) {
        for (int j = 0; j < 6; j++) {
            cin >> arr[i][j];
        }
    }
    int ans = 0;
    while (1) {
        bool flag = bfs();
        if (flag) {
            break;
        }
        gravity();
        ans++;
    }
    cout << ans;
    return 0;
}