PROGRAMMING:Output centigrade Fahrenheit temperature conversion table

Enter 2 positive integers lower and upper (- 20 < = lower < = upper < = 50) to represent the centigrade range. Please output one with the value range of [lower, upper]
And each time increase 2 degrees Celsius - Fahrenheit temperature conversion table. The calculation formula of temperature conversion is as follows
F=C × 1.8+32
Where C is the temperature in centigrade and F is the temperature in Fahrenheit.
###Input format:
Enter two integers in one line to represent the values of lower and upper, separated by spaces.
###Output format:
The first line output: "Celsius $$\ box / box / box $$Fahr"
Then output a Celsius (integer) and a Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit Fahrenheit fahren.
If the input range is illegal, output "invalid.".
###Input sample 1:
Here is a set of inputs. For example:
```in
2 9
```
###Output sample 1:
The corresponding output is given here. For example:
```out
celsius fahr
2 35.6
4 39.2
6 42.8
8 46.4
```
###Input sample 2:
Here is a set of inputs. For example:
```in
2 51
```
###Output sample 2:
The corresponding output is given here. For example:
```out
Invalid.
```







answer：If there is no answer, please comment
```
lower,upper=input().split()
lower,upper=int(lower),int(upper)
if lower<-20 or upper>50:
print("Invalid.")
else:
print("celsius fahr")
for i in range(lower,upper,2):
f=i*1.8+32
print("{:d}{:14.1f}".format(i,f))
```