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EQUITY - Treasury stocks (Details) - BRL (R$) R$ / shares in Units, R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Capital |  |  |
Number of shares outstanding at end of period | 1,698,941,000 |  |
Equity at beginning of period | R$ 25,938,571 | R$ 23,893,941 | R$ 24,274,653
Repurchases |  | 243,723 |
Exercise of stock options | 29,411 | 23,354 | 19,682
Transfer of shares |  | 18,984 |
Equity at end of period | R$ 27,173,127 | R$ 25,938,571 | R$ 23,893,941
Investments and working capital reserve |  |  |
Investments and working capital reserve, annual percentage | 5.00% |  |
Common shares |  |  |
Capital |  |  |
Number of shares outstanding at beginning of the year | 571,929,945 | 571,929,945 | 571,929,945
Number of shares outstanding at end of period | 571,929,945 | 571,929,945 | 571,929,945
Preferred shares |  |  |
Capital |  |  |
Number of shares outstanding at beginning of the year | 1,124,233,755 | 1,137,327,184 | 1,137,018,570
Repurchases |  | 16,000,000 |
Exercise of long-term incentive plan | 2,777,072 | 1,597,235 | 308,614
Transfer of shares |  | 1,309,336 |
Number of shares outstanding at end of period | 1,127,010,827 | 1,124,233,755 | 1,137,327,184
Treasury Stocks |  |  |
Capital |  |  |
Equity at beginning of period | R$ (280,426) | R$ (76,085) | R$ (98,746)
Repurchases |  | 243,396 |
Exercise of stock options | 37,884 | 27,433 | 22,661
Transfer of shares |  | 11,622 |
Equity at end of period | R$ (242,542) | R$ (280,426) | R$ (76,085)
Average acquisition cost | R$ 12.72 | R$ 12.84 | R$ 8.68
Treasury Stocks | Common shares |  |  |
Capital |  |  |
Number of shares outstanding at beginning of the year | 1,697,538 | 1,697,538 | 1,697,538
Number of shares outstanding at end of period | 1,697,538 | 1,697,538 | 1,697,538
Equity at beginning of period | R$ 557 | R$ 557 | R$ 557
Equity at end of period | R$ 557 | R$ 557 | R$ 557
Treasury Stocks | Preferred shares |  |  |
Capital |  |  |
Number of shares outstanding at beginning of the year | 21,797,490 | 8,704,061 | 9,012,675
Repurchases |  | 16,000,000 |
Exercise of long-term incentive plan | (2,777,072) | (1,597,235) | (308,614)
Transfer of shares |  | (1,309,336) |
Number of shares outstanding at end of period | 19,020,418 | 21,797,490 | 8,704,061
Equity at beginning of period | R$ 279,869 | R$ 75,528 | R$ 98,189
Repurchases |  | 243,396 |
Exercise of stock options | (37,884) | (27,433) | (22,661)
Transfer of shares |  | (11,622) |
Equity at end of period | R$ 241,985 | R$ 279,869 | R$ 75,528

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