import java.util.*;

public class Main {
    static final int MOD = 1000000007;
	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 c = sc.nextLong();
		    long d = sc.nextLong() % MOD;
		    ans += (c + 1) / 2 % MOD * d % MOD;
		    ans %= MOD;
		}
		System.out.println(ans);
	}
}