Question: 
Write a python function to count the maximum number of equilateral triangles that can be formed within a given equilateral triangle.


Model's Code:
def No_of_Triangle(side_length, triangle_side):
    if triangle_side > side_length:
        return -1
    num = (side_length - triangle_side + 1) * (side_length - triangle_side) // 2
    return num



Sample Correct Code:
def No_of_Triangle(N,K):
    if (N < K):
        return -1;
    else:
        Tri_up = 0;
        Tri_up = ((N - K + 1) *(N - K + 2)) // 2;
        Tri_down = 0;
        Tri_down = ((N - 2 * K + 1) *(N - 2 * K + 2)) // 2;
        return Tri_up + Tri_down;


Asserts:
assert No_of_Triangle(4,2) == 7
assert No_of_Triangle(4,3) == 3
assert No_of_Triangle(1,3) == -1


Tests:
Test 1 of 3: FAIL: AssertionError()

Test 236 of 974: 171/236 (72.45762711864407%): failed