I use :
int a[ 100000 ];
short num[ 100000 ];
And I have MLE #1!!!

100000 * 4 + 100000 * 2 = 600000 bytes + plus memory for your programm.
Memory limit can be 750000 bytes instead of 750 Kb.

How to avoid MLE???

You use too much memory. Try to fit into one array int[100000]...

Can you prompt me? I can't think up how to do it.

For example, look at corresponding section in D. Knuth's book (something about several stacks in one memory segment)

I can't find it!? Can you tell me any idea???

Just use the "realloc()" function ;-)