You would be writing values in space you did not reserve for that purpose.
If you were lucky, the operating system would notice and give you a 
segmentation violation (A GPF under Microsoft Windows). 

If you were unlucky, you would change the value of other variables (since
they are just memory locations) to strange values and get really 
weird behavior (like an infinite loop if the index in a for-loop got
set to zero somewhere in the middle of the loop range!).

There is no real "solution" to this exercise...