package no146;

import java.util.Scanner;

public class Main {

	static final long MOD = 1000000007;
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long ans = 0;
		for(int i=0;i<n;i++) {
			long c = (Long.parseLong(sc.next()) + 1) / 2 % MOD;
			long d = Long.parseLong(sc.next()) % MOD;
			ans = (ans + c * d) % MOD;
		}
		System.out.println(ans);
	}

}