Select the number that will replace the question mark (?) in the following number series.
$$1,1,2,3,5,8,13,?$$

This sequence is the standard Fibonacci sequence, where every term starting from the third position is computed as the sum of its two immediately preceding numbers:
* $1+1=2$
* $1+2=3$
* $2+3=5$
* $3+5=8$
* $5+8=13$

Following this logic, the next value is:

$$8+13=21$$