import java.math.*;
import java.util.*;

class Main {
	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 a =(sc.nextLong()+1)/2%1000000007;
        	long b = sc.nextLong();
        	ans=(ans+(a+1)/2*b)%1000000007;
        }
        System.out.println(ans);
	}
}