/******************************************************************************
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import java.util.*;
public class Main
{
static int singleNumber(int [] nums) {
TreeSet<Integer> seen = new TreeSet<Integer>();
TreeSet<Integer> unseen = new TreeSet<Integer>();
for(int num:nums) {
if(seen.contains(num))
unseen.remove(num);
else
unseen.add(num);
seen.add(num);
}
return unseen.first();
}
public static void main(String[] args) {
System.out.println(String.format("%d", singleNumber(new int[]{1,3,3,1,3,4})));
}
}
