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 __add__(self, other):
        if self.rows != other.rows or self.cols != other.cols:
            raise ValueError("Matrices must have the same dimensions for addition.")
        result = [[self.data[i][j] + other.data[i][j] for j in range(self.cols)] for i in range(self.rows)]
        return Matrix(result)

    def __mul__(self, other):
        if self.cols != other.rows:
            raise ValueError("Number of columns in the first matrix must be equal to the number of rows in the second matrix.")
        result = [[sum(self.data[i][k] * other.data[k][j] for k in range(self.cols)) for j in range(other.cols)] for i in range(self.rows)]
        return Matrix(result)

    def transpose(self):
        result = [[self.data[j][i] for j in range(self.rows)] for i in range(self.cols)]
        return Matrix(result)

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

# 示例使用
m1 = Matrix([[1, 2], [3, 4]])
m2 = Matrix([[5, 6], [7, 8]])
print("Matrix 1:")
print(m1)
print("Matrix 2:")
print(m2)
print("Matrix 1 + Matrix 2:")
print(m1 + m2)
print("Matrix 1 * Matrix 2:")
print(m1 * m2)
print("Transpose of Matrix 1:")
print(m1.transpose())