Sum of Prime Numbers Up to N

Calculate the sum of all prime numbers less than or equal to a given positive integer n. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

Method Signature

public static Integer sumOfPrimes(Integer n)

Examples

Example 1:

Input: n = 10
Output: 17
Explanation: The prime numbers less than or equal to 10 are 2, 3, 5, 7. Their sum is 2 + 3 + 5 + 7 = 17.

Example 2:

Input: n = 5
Output: 10
Explanation: The prime numbers less than or equal to 5 are 2, 3, 5. Their sum is 2 + 3 + 5 = 10.

Example 3:

Input: n = 2
Output: 2
Explanation: The only prime number less than or equal to 2 is 2 itself.

Example 4:

Input: n = 1
Output: 0
Explanation: There are no prime numbers less than or equal to 1.

Example 5:

Input: n = null
Output: null
Explanation: Return null for null input.

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