map, filter, reduce

These three operations are the backbone of data transformation. Most data pipelines boil down to some combination of them.

• map — transform each element
• filter — keep only elements matching a condition
• reduce — collapse all elements into one value

Given a list of integers, apply this pipeline in order:

1. Filter out any numbers less than 0
2. Map each remaining number to its square
3. Reduce the squares to their sum

Print the final sum. If the list is empty after filtering, print 0.

Input:  3,-1,4,-1,5,9
Output: 131   // 3²+4²+5²+9² = 9+16+25+81 = 131

Constraints

• Implement each step separately — don't combine them into one loop.
• Numbers are comma-separated integers.