1.  term = 3
2.  n1, n2, n3 = 3, 5, 4
3.  grades = ([0] * term)
4.  grades[0] = ([0] * n1)
5.  grades[1] = ([0] * n2)
6.  grades[2] = ([0] * n3)
7.  grades[0] = [15, 18, 12]
8.  grades[1] = [18, 14, 17, 19, 16]
9.  grades[2] = [16, 15, 10, 18]
10. sumgrades = 0
11. ave = 0.0
12. for i in range(len(grades)):
13.    for j in range(len(grades[i])):
14.        sumgrades += grades[i][j] * 3
15. ave =  sumgrades / ((n1 + n2 + n3) *3)
16. print("average = ", ave)