import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        long ans = 0;
        long mod = 1000000007;

        for(int i=0; i<n; i++) {
            long c = in.nextLong();
            long d = in.nextLong();
            ans += ((c+1) / 2 % mod * (d%mod)) % mod;
            ans %= mod;
        }

        System.out.println(ans);
    }
}