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At line 52 you have a index value that is past the end for the array on that line.
The array has less than 3 elements.
Check you logic to see how the index gets to the value of 2.
Remember that...

You must assign values to each slot in the array:
array[ix] = aValue; // set element ix to aValue

You should Try reading the tutorial.
Go to this site:...

There is no easy way to tell until you get it all together.
You will be able to tell when you get a definition for that class and can compile the program and exectute it and have it do what you want.

What should arreglo look like?
It should be defined as a class:
class arreglo {
//?????
} // end of class
And it needs to have all the methods that are used in the code:
...

The "cannot find symbol" message means that the compiler can not find a definition for the symbol mentioned in the error message.
Where is the class: arreglo defined? The compiler can not find it.