第四题：

int helper(int i, int j, int x, int y, int k, vector<vector<char>> &graph) {
    for (int a = 0; a < k; a++) {
        for (int b = 0; b < k; b++) {
            if (graph[i + a][j + b] != graph[x + a][y + b]) {
                k = min(k, b);
            }
        }
    }
    return k;
}

int main() {
    int n, m;
    cin >> n >> m;
    vector<vector<char>> graph(n, vector<char>(m));
    vector<vector<pair<int, int>>> hash(26);
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cin >> graph[i][j];
            hash[graph[i][j] - 'a'].push_back(make_pair(i, j));
        }
    }
    int i, j, x, y, k, temp;
    int res = 0;
    vector<int> re(4);
    for (int t = 0; t < 26; t++) {
        for (int a = 0; a < hash[t].size(); a++) {
            for (int b = a + 1; b < hash[t].size(); b++) {
                i = hash[t][a].first;
                j = hash[t][a].second;
                x = hash[t][b].first;
                y = hash[t][b].second;
                k = min(min(n - i, m - j), min(n - x, m - y));
                temp = helper(i, j, x, y, k, graph);
                if (temp > res) {
                    res = temp;
                    re[0] = i;
                    re[1] = j;
                    re[2] = x;
                    re[3] = y;
                }
            }
        }
    }
    if (res != 0) {
        cout << res << endl;
        cout << re[0] + 1 << ' ' << re[1] + 1 << endl;
        cout << re[2] + 1 << ' ' << re[3] + 1 << endl;
    }
    else
        cout << 0 << endl;

    system("pause");
    return 0;
}