The problem statement is to find the numbers between a String and find the appropriate character for the given number. To be specific, 0 represents 'a', 1 represents 'b', 2 represents 'c'... like so on. And then again 26 represents 'a', 27- 'b', 28- 'c'....goes on like this.

For better understanding:

```
Input String: ab1ab

Output: b

```

Explanation: there is one integer value '1' in the string which represents 'b'.

```
Input String 2: abcd00hdjhs1224

Output: ac

```

Explanation: there are two integer values '00' and '1224' which represent 'a' and 'c' respectively.

The problem with my solution was that when I was storing the integer values into int or long data type, large values threw NumberFormatException.

What would be a better approach to overcome this problem? More than a programming problem it's algorithmic problem. How can I achieve the solution without worrying about the large number or the BigInteger class?

Note: If multiple integers occur then the whole is considered as one integer value.(That is where the problem occurs for me)