Overview

This problem asks us to find the sum of the digits of a membership number \(N\). We can read \(N\) as a string, convert each character to an integer one by one, and add them up.

Analysis

When treating a base-10 integer as a string, each character directly corresponds to each digit.

For example, if we read \(N = 2024\) as the string "2024", we can extract "2", "0", "2", and "4" in order. Converting each to an integer and summing them gives \(2 + 0 + 2 + 4 = 8\).

For this problem, a naive approach of examining each digit sequentially is sufficient. Since \(N \leq 10^9\), the number of digits is at most \(10\), so the execution time is not an issue.

However, since the read characters are strings, they cannot be added directly as numerical values. Each character must be converted to an integer using int().

Algorithm

1. Read \(N\) as a string.
2. Convert each character of the string to an integer.
3. Sum the converted integers using sum() and print the result.

Since each digit is added exactly once, the resulting sum matches the definition of the lucky number.

Complexity

Let \(D\) be the number of digits of \(N\).

• Time Complexity: \(O(D)\)
• Space Complexity: \(O(D)\)

Storing the input string takes \(O(D)\) space. The additional space used for computing the sum is \(O(1)\).

Implementation Notes

• input().strip() reads the input as a string and removes leading and trailing whitespace.

• int(c) for c in N is a generator expression that converts each character c of the string N to an integer.

• By passing it to sum(), we can sum the converted integers directly without storing them in a list.

• The digit 0 is also correctly converted by int("0"), so no special handling is required.

  Source Code

N = input().strip()
print(sum(int(c) for c in N))

---

This editorial was generated by gpt-6-astra-medium.