import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long MOD = (long)Math.pow(10, 9) + 7;
    int N = sc.nextInt();
    long ans = 0;
    for(int i = 0; i < N; i++) {
      long c = sc.nextLong();
      long d = sc.nextLong();
      c = ((c + 1) / 2) % MOD;
      d = d % MOD;
      ans = (ans + c * d) % MOD;
    }
    System.out.println(ans);
  }
}