import java.util.*;
import java.math.*;
import java.io.*;
public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long sum = 0L;
		for(int i = 0; i < n; i++) {
			long c = sc.nextLong() % 1000000007;
			long d = sc.nextLong() % 1000000007;
			sum += d * (c/2 + 1 -(c%2==0?1:0)) % 1000000007;
			sum %= 1000000007;
		}
		System.out.println(sum);
		
	}
 }