
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
For the quadrilateral shown, how many different whole numbers could be the length of the diagonal represented by the dashed line?

[asy]
draw((0,0)--(7,7)--(15,2)--(9,-10)--cycle,linewidth(0.7));
draw((0,0)--(15,2),dashed);
label("11",(3.5,3.5),NW);
label("13",(11,4.5),NE);
label("21",(12, -4),SE);
label("15",(4.5,-4),SW);
[/asy]

Present the answer in LaTex format: \boxed{Your answer}
user