# Dropped Sensor Metric

You are given two lists of integers `a`

and `b`

representing sensor metrics. Each list contains unique integers and `a ≠ b`

. One of the lists contains accurate sensor metrics but the other one is faulty. In the faulty list one number that wasn’t the last number was dropped and a fake value was appended to the end of the list. Return the number that was dropped.

**Constraints**

`2 ≤ n ≤ 100,000`

where`n`

is the length of`a`

and`b`

https://binarysearch.com/problems/Dropped-Sensor-Metric

## Examples

### Example 1

**Input**

- a =
`[1, 2, 3]`

- b =
`[2, 3, 5]`

**Output**

- answer =
`1`

**Explanation**

The accurate metrics come from `a = [1, 2, 3]`

.

### Example 2

**Input**

- a =
`[5, 4, 2, 1, 6]`

- b =
`[5, 4, 3, 2, 1]`

**Output**

- answer =
`3`

**Explanation**

The accurate metrics come from `b = [5, 4, 3, 2, 1]`

.

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