import java.math.BigInteger;
import java.util.Scanner;


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