import java.util.Scanner;

public class Main {
	public static void main(String[] a) {
		Scanner s = new Scanner(System.in);
		long N=s.nextInt(),i=0,z=0,c;
		while(i++<N)z+=(((c=s.nextLong())/2+c%2)%(1E9+7)*s.nextLong()%(1E9+7))%(1E9+7);
		System.out.println(z);
	}
}