Create a diagonal matrix with elements from N to 0. Count the sum of its values on the diagonal.

def create_diag_matrix(n):

    #create a list of lists first
    return  [[0 for _ in range(n)] for _ in range(n)]


def create_diag_matrix_2(n):
    return [[i*0+1 if i==j else i*0 for i in range(n)] for j in range(n)]

def create_diag_matrix_3(n):
    return [[1 if i==j else 0 for i in range(n)] for j in range(n)]