The following is a summary of activity for common stock warrants for the year ended December 31, 2013:
| Common stock warrants |
Weighted- average exercise price |
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|
Outstanding, January 1, 2013 |
1,086,343 | $ | 0.83 | |||||
|
Granted |
110,401 | 1.70 | ||||||
|
Exercised |
(332,189) | 0.03 | ||||||
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Outstanding, December 31, 2013 |
864,555 | $ | 1.04 | |||||
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