from typing import List
import math

def matmul(mat_a: List[List[float]], mat_b: List[List[float]]) -> List[List[float]]:
    m, n = len(mat_a), len(mat_a[0])
    n2, p = len(mat_b), len(mat_b[0])

    # Dimension prüfen: Spaltenzahl von A == Zeilenzahl von B
    if n != n2:
        raise ValueError('Matrix dimensions do not match')

    result = []
    for i in range(m):            # Zeilen von A
        line = []
        for j in range(p):        # Spalten von B
            s = 0.0
            for k in range(n):    # Spalten von A / Zeilen von B
                s += mat_a[i][k] * mat_b[k][j]  # <--- wichtig: b[k][j]
            line.append(s)
        result.append(line)
    return result


if __name__ == "__main__":
    matrix_a = [
        [3, 4, -1, 4],
        [-2, 2, 5, 1]
    ]

    matrix_b = [
        [1, 3, -2],
        [2, 5, 1],
        [-1, 4, -4],
        [2, 3, 6]
    ]

    matrix_c = matmul(matrix_a, matrix_b)
    print("Ergebnis C = A * B:")
    for row in matrix_c:
        print(row)