Help mi out wats wrong with this code

Question

# Write your code
print("calculater")
operator = input("enter operator either +, -, *, or divide")
n1 = float(input("frist_number:"))
n2 = float(input("second_number:"))
if_operator == '+':
print(n1, operator, n2, '+', n1+n2)
elif operator == '/' :
print(n1, operator, n2, '/', n1/n2)
elif operator == '*' :
print(n1, operator, n2, '*', n1*n2)
else:
print("invalid ")