class Matrix:
    def __init__(self, data):
        self.data = data
        self.rows = len(data)
        self.cols = len(data[0]) if self.rows > 0 else 0

    def multiply(self, other):
        if self.cols != other.rows:
            raise ValueError("The number of columns in the first matrix must be equal to the number of rows in the second matrix.")

        result = [[0 for _ in range(other.cols)] for _ in range(self.rows)]

        for i in range(self.rows):
            for j in range(other.cols):
                for k in range(self.cols):
                    result[i][j] += self.data[i][k] * other.data[k][j]

        return Matrix(result)

    def __str__(self):
        return 'n'.join([' '.join(map(str, row)) for row in self.data])

# 示例使用
matrix1 = Matrix([[1, 2, 3], [4, 5, 6]])
matrix2 = Matrix([[7, 8], [9, 10], [11, 12]])

result_matrix = matrix1.multiply(matrix2)
print(result_matrix)