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LONG-TERM INCENTIVE PLANS - Exercise of stock options (Details) - Stock options | Dec. 31, 2018 BRL (R$) Y Options | Dec. 31, 2017 BRL (R$) Options | Dec. 31, 2016 BRL (R$) Options | Dec. 31, 2015 BRL (R$) Options
--- | --- | --- | --- | ---
Exercise price of options |  |  |  |
Quantity (in shares) | 15,480 | 292,391 | 569,115 | 1,074,246
Average exercise price | R$ | R$ 16.72 | R$ 17.91 | R$ 16.64 | R$ 18.36
Number exercisable at end of the period (in shares) | 15,480 | 57,668 | 57,678 |
R$ 16.86 |  |  |  |
Exercise price of options |  |  |  |
Exercise price | R$ | R$ 16.86 |  |  |
Quantity (in shares) | 10,754 |  |  |
Average period of grace (in years) | Y | 0.2 |  |  |
Average exercise price | R$ | R$ 15.90 |  |  |
Number exercisable at end of the period (in shares) | 10,754 |  |  |
R$ 18.58 |  |  |  |
Exercise price of options |  |  |  |
Exercise price | R$ | R$ 18.58 |  |  |
Quantity (in shares) | 4,726 |  |  |
Average period of grace (in years) | Y | 4.0 |  |  |
Average exercise price | R$ | R$ 18.58 |  |  |
Number exercisable at end of the period (in shares) | 4,726 |  |  |

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