import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.TreeSet;

public class Main {
	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		final int N = sc.nextInt();
		final long MOD = 1000000007;
		
		long sum = 0;
		for(int i = 0; i < N; i++){
			final long C = sc.nextLong();
			final long D = sc.nextLong();
			
			sum += (C + 1) / 2 * D;
			sum %= MOD;
		}
		
		System.out.println(sum);
	}
}