import java.io.*;
import java.util.stream.*;
public class Ludo {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		int N = Integer.valueOf(in.readLine()), i = N;
		long[] C = new long[N];
		while (i --> 0)
			C[i] = Stream.of(in.readLine().split(" ")).mapToLong(Long::valueOf).sum();
		System.out.println(LongStream.of(C).sum()/2L - LongStream.of(C).sorted().limit(N/2).sum());
	}
}