#write a program that reads one positive 4-digit number
#and prints the sum of the digits

#additional task: at the end of the program we also want to print an original 
#input. To implement this we will use an additional variable and save
#original value before calculations.

#Discussion:
#Input:integer, between 1000 and 9999 stored in variable num
#Output: sum of digits, stored in variable sum
#Calculations: int division by 10 and modulo 10 to separate digits and then
#add digits together
#Input Limitations: integer, between 1000 and 9999 

#Part 1 Input:

num=int(input("enter integer between 1000 and 9999: "))

#Part 2 Calculation:
#Let's call digits d1, d2, d3, d4 where d1 is first digit and d4 is last digit

save_num = num #saving an original value

d4 = num%10
num = num//10
d3 = num%10
num = num//10
d2= num%10
num = num//10
d1= num%10

sum = d1+d2+d3+d4

#Part 3 Output

print("sum of digits of", save_num , "is", sum)