The 2025-2026 ICPC RSU High School Programming Contest

Problem Statement

Given a positive integer, calculate the sum of its digits. For example, the sum of digits for 123 is 6 (1 + 2 + 3).

Input

A single positive integer n (1 ≤ n ≤ 10^9).

Output

The sum of the digits of n.

Sample Input

123

Sample Output

6

Solution Approach

To solve this problem, you can repeatedly extract the last digit of the number using modulo 10 operation, add it to the sum, and then remove the last digit by dividing the number by 10 (integer division). Repeat this process until the number becomes 0.

Problem Statement

Write a program that determines whether a given integer is even or odd.

Input

A single integer n (-10^9 ≤ n ≤ 10^9).

Output

Print "Even" if the number is even, or "Odd" if the number is odd.

Sample Input

7

Sample Output

Odd

Solution Approach

An integer is even if it's divisible by 2 (i.e., n % 2 == 0), and odd otherwise. Note that this works for both positive and negative numbers.

Problem Statement

Determine if a given string is a palindrome (reads the same forwards and backwards). Ignore case and non-alphanumeric characters.

Input

A string s (1 ≤ length(s) ≤ 1000).

Output

Print "True" if the string is a palindrome, "False" otherwise.

Sample Input

"A man, a plan, a canal: Panama"

Sample Output

True

Solution Approach

First, process the string to remove non-alphanumeric characters and convert to lowercase. Then use two pointers (one at start, one at end) moving towards each other, comparing characters until they meet in the middle.

Problem Statement

Write a program to calculate the factorial of a non-negative integer n (n!).

Input

A single non-negative integer n (0 ≤ n ≤ 20).

Output

The factorial of n.

Sample Input

5

Sample Output

120

Solution Approach

The factorial of n is the product of all positive integers less than or equal to n. Note that 0! is 1. You can solve this with either iteration (for/while loop) or recursion.

Problem Statement

Given a number n, print all prime numbers less than or equal to n using the Sieve of Eratosthenes algorithm.

Input

A single integer n (2 ≤ n ≤ 10^6).

Output

All prime numbers ≤ n, separated by spaces.

Sample Input

20

Sample Output

2 3 5 7 11 13 17 19

Solution Approach

The Sieve of Eratosthenes works by iteratively marking the multiples of each prime number starting from 2. Create a boolean array where each index represents whether the number is prime, then mark non-primes as you find them.

Problem Statement

Write a program that prints the first n numbers in the Fibonacci sequence, both iteratively and recursively.

Input

A single integer n (1 ≤ n ≤ 20).

Output

Two lines: first line shows the sequence using iteration, second line shows it using recursion.

Sample Input

8

Sample Output

0 1 1 2 3 5 8 13
0 1 1 2 3 5 8 13

Solution Approach

The Fibonacci sequence starts with 0 and 1, and each subsequent number is the sum of the previous two. For iteration, use a loop to build the sequence. For recursion, implement the mathematical definition directly (but note that recursive solution is inefficient for large n).