Triangle - Python

import math
a = float(input('Enter a: '))
b = float(input('Enter b: '))
c = float(input('Enter c: '))

if a <= 0 or b <= 0 or c <= 0 or a + b <= c or a + c <= b or b + c <= a:
    print('Invalid triangle')
else:
    P = a + b + c
    p = P / 2
    S = math.sqrt(p*(p-a)*(p-b)*(p-c))
    print('P = ' + str(P))
    print('S = ' + str(S))