import java.util.Scanner;

class Main{
	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		long n=stdIn.nextLong(),c,d,s=0,i;
		for(i=0;i<n;i++) {
			c=stdIn.nextLong();
			d=stdIn.nextLong();
			s=(s+((c+1)/2%1000000007)*(d%1000000007))%1000000007;
		}
		System.out.print(s);
	}
}