void readMatrix(float **&matrix, int &n) {
    //odczytywanie z pliku
    ifstream file;
    string filename;
    cin >> filename;
    file.open(filename);
    if (file.good()) {
        string row;
        bool row1 = false;
        int i = 0;
        while (getline(file, row)) {
            if (!row1) {
                row1 = true;
                int amount = count(row.begin(), row.end(), ';');
                if (matrix != NULL)
                    deleteMatrix(matrix, n);
                makeMatrix(matrix, amount);
                n = amount;
            }
            istringstream columns(row);
            string column;
            int j = 0;
            while (getline(columns, column, ';')) {
                matrix[i][j] = atof(column.c_str());
                j++;
            }
            i++;
        }
        file.close();
    }
    else cout << "Nie ma dostępu do pliku." << endl;
}