Polygon area

vertices = int(input())
prod1 = 0
prod2 = 0

for i in range(vertices):
    x, y = map(int, input().split())

    if i == 0:
        x1 = x
        y1 = y
    else:
        prod1 += prev_x * y
        prod2 += prev_y * x

    prev_x = x
    prev_y = y

prod1 += x * y1
prod2 += y * x1

print(abs(prod1 - prod2))

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED