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EQUITY - Treasury stocks (Details) - BRL (R$) R$ / shares in Units, R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Value of shares |  |  |
Balance at beginning of period | R$ 27,173,127 | R$ 25,938,571 | R$ 23,861,554
Repurchases |  |  | 243,723
Exercise of stock options | 9,596 | 29,411 | 23,354
Transfer of shares |  |  | 18,984
Balance at end of period | R$ 31,085,210 | R$ 27,173,127 | R$ 25,938,571
Common shares |  |  |
Number of shares |  |  |
Balance at beginning of the year | 571,929,945 | 571,929,945 | 571,929,945
Balance at end of period | 571,929,945 | 571,929,945 | 571,929,945
Preferred shares |  |  |
Number of shares |  |  |
Balance at beginning of the year | 1,127,010,827 | 1,124,233,755 | 1,137,327,184
Repurchases |  |  | 16,000,000
Exercise of long-term incentive plan | 2,220,660 | 2,777,072 | 1,597,235
Transfer of shares |  |  | 1,309,336
Balance at end of period | 1,129,231,487 | 1,127,010,827 | 1,124,233,755
Treasury Stocks |  |  |
EQUITY |  |  |
Average acquisition cost | R$ 13.62 | R$ 12.72 | R$ 12.84
Value of shares |  |  |
Balance at beginning of period | R$ (242,542) | R$ (280,426) | R$ (76,085)
Repurchases |  |  | 243,396
Exercise of stock options | 13,233 | 37,884 | 27,433
Transfer of shares |  |  | 11,622
Balance at end of period | R$ (229,309) | R$ (242,542) | R$ (280,426)
Treasury Stocks | Common shares |  |  |
Number of shares |  |  |
Balance at beginning of the year | 1,697,538 | 1,697,538 | 1,697,538
Balance at end of period | 1,697,538 | 1,697,538 | 1,697,538
Value of shares |  |  |
Balance at beginning of period | R$ 557 | R$ 557 | R$ 557
Balance at end of period | R$ 557 | R$ 557 | R$ 557
Treasury Stocks | Preferred shares |  |  |
Number of shares |  |  |
Balance at beginning of the year | 19,020,418 | 21,797,490 | 8,704,061
Repurchases |  |  | 16,000,000
Exercise of long-term incentive plan | (2,220,660) | (2,777,072) | (1,597,235)
Transfer of shares |  |  | (1,309,336)
Balance at end of period | 16,799,758 | 19,020,418 | 21,797,490
Value of shares |  |  |
Balance at beginning of period | R$ 241,985 | R$ 279,869 | R$ 75,528
Repurchases |  |  | 243,396
Exercise of stock options | (13,233) | (37,884) | (27,433)
Transfer of shares |  |  | (11,622)
Balance at end of period | R$ 228,752 | R$ 241,985 | R$ 279,869

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