public static int lonelyinteger(List<Integer> a) {
        // Sort list
        Collections.sort(a);
        //   Return first elem if size is one or second elem doesn't match
        int ans=a.get(0);
        if(a.size()==1 || a.get(0) != a.get(1))
                return ans;
        // Iterate through list
        for(int i=1;i<a.size()-1;i++) {
        // Compare num before and after from index 1 - size-1
                if(a.get(i)!= a.get(i-1) && a.get(i)!= a.get(i+1)){
        // If unequal return elem
                        return a.get(i);                
                }
        }
        // If each elem has match but last return last
        return a.get(a.size()-1);            
}