/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
List<Integer> sequence = new ArrayList<Integer>();
sequence.add(4);
sequence.add(5);
sequence.add(7);
sequence.add(8);
int match = 0;
int first = sequence.get(0); // sets the first value in seq. to var
int size = sequence.size(); // sets the seq size to var
for (int i = 0; i < size; i++)
{
    if ((first + i) != sequence.get(i)) {
        match = (first + i);
        break;
    }
}
System.out.println(match + " is not in the sequence.");
 
	}
}

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