human
schlumberger limited and subsidiaries shares of common stock issued in treasury shares outstanding (stated in millions).
|  | Issued | In Treasury | Shares Outstanding |
| --------- | --------- | --------- | --------- |
| Balance, January 1, 2008 | 1,334 | (138) | 1,196 |
| Shares sold to optionees less shares exchanged | – | 5 | 5 |
| Shares issued under employee stock purchase plan | – | 2 | 2 |
| Stock repurchase program | – | (21) | (21) |
| Issued on conversions of debentures | – | 12 | 12 |
| Balance, December 31, 2008 | 1,334 | (140) | 1,194 |
| Shares sold to optionees less shares exchanged | – | 4 | 4 |
| Vesting of restricted stock | – | 1 | 1 |
| Shares issued under employee stock purchase plan | – | 4 | 4 |
| Stock repurchase program | – | (8) | (8) |
| Balance, December 31, 2009 | 1,334 | (139) | 1,195 |
| Acquisition of Smith International, Inc. | 100 | 76 | 176 |
| Shares sold to optionees less shares exchanged | – | 6 | 6 |
| Shares issued under employee stock purchase plan | – | 3 | 3 |
| Stock repurchase program | – | (27) | (27) |
| Issued on conversions of debentures | – | 8 | 8 |
| Balance, December 31, 2010 | 1,434 | (73) | 1,361 |
see the notes to consolidated financial statements part ii, item 8.
Please answer the following questions with expressions if necessary.
what was the balance of shares at the end of 2008?
assistant
1194
human
what was the balance of shares at the end of 2009?
assistant
1195
human
what is the sum?
assistant
add(1194, 1195)
human
what is the average number of shares?
assistant
add(1194, 1195), divide(#0, const_2)