Why this gives me syntax error?

Question

print("||Wellcome To Python||")
str = input("Weight and Hieght")
a,b = str.split(' ')
print('Your BMI is',int(a) / ((int(b))**2))
int(a) = int(a) / (int(b)**2
if (a > 25)
print("Fat!")
elif (a > 20 & a < 25)
print("Good!")
elif (a < 20)
print("Thin!")
input("Press Space to finish...")

Answer 1

If statements in python don't require parentheses, but do require a colon after the statement declaration:
if a > 25 :
print("Fat")

Answer 2

thank you very much!