行列の２乗

arr = [[0 for i in range(4)] for j in range(4)]
arr2 = [[0 for i in range(4)] for j in range(4)]
#print(arr)
for i in range(4):
    for j in range(4):
        x = input("Please Enter [" + str(i) +  "][" + str(j) +  "] Number: ")
        arr[i][j] = int(x)

for i in range(4):
    for j in range(4):
        for k in range(4):
            arr2[i][j] += arr[i][k] * arr[k][j]

for i in range(4):
    print(str(arr2[i][0]) + " " +
        str(arr2[i][1]) + " " +
        str(arr2[i][2]) + " " +
        str(arr2[i][3]))
input("\nPress any key to exit.")