java快读快写都过不了，有人过的了么？

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;

public class Main {
	public static void main(String[] args) throws Exception{
		StreamTokenizer st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
		PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
		st.nextToken();
		int n = (int)st.nval;
		int ans = 0;
		for(int i=0;i<n;i++) {
			st.nextToken();
			ans ^= (int)st.nval;
		}
		pw.println(ans);
	}
}