Implement mean squared error

Given two lists of predictions and targets (same length), compute the mean squared error: (1/n) * sum((pred[i] - target[i])^2).

Input: Two lines. First: space-separated predictions. Second: space-separated targets.

Output: One number (MSE), rounded to 4 decimal places.

Example:

• Input: 1 2 3 and 1 2 4
• Output: 0.3333 (only last element differs: (3-4)^2 = 1, mean = 1/3)