Table:
|  | Number of Shares (thousands) | Weighted-Average Exercise Price | Weighted-Average Remaining Contractual Term (years) | Aggregate Intrinsic Value(1) (thousands) |
| --- | --- | --- | --- | --- |
| Outstanding as of December 31, 2018 | 4,674 | $5.19 |  |  |
| Granted | — | $ — |  |  |
| Exercised | (842) | $2.84 |  |  |
| Canceled | (130) | $9.41 |  |  |
| Outstanding as of December 31, 2019 | 3,702 | $5.57 | 3.52 | $6,395 |
| Vested and exercisable as of December 31, 2019 | 3,427 | $5.49 | 3.56 | $6,210 |
Paragraphs:
Stock options
The following tables summarize our stock option activities and related information:
(1) The aggregate intrinsic value represents the excess of the closing price of our common stock of $6.87 as of December 31, 2019 over theexercise price of the outstanding in-the-money options.
Question:
What is the number of shares exercised as of December 31, 2018? 
Answer: (842)