import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner koko = new Scanner(System.in);
		int n = koko.nextInt();
		long[] c = new long[n];
		long[] d = new long[n];
		for (int i = 0; i < n; i++) {
			c[i] = koko.nextLong();
			d[i] = koko.nextLong();
		}
		long total = 0;
		System.out.println(total);
	}
}