import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.math.BigInteger;

public class Main {
	public static void main(String[] args) {
		BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
		try {
			int count = Integer.parseInt(read.readLine());
			BigInteger ans = new BigInteger("0");
			while (count-- > 0) {
				String[] box = read.readLine().split(" ");
				int add = 0;
				if ((Long.parseLong(box[0]) % 2) == 1) {
					add = 1;
				}
				BigInteger fir = new BigInteger("" + ((Long.parseLong(box[0]) / 2) + add));
				ans = ans.add(fir.multiply(new BigInteger(Long.parseLong(box[1]) + "")));
				ans = ans.mod(new BigInteger("1000000007"));
			}

			System.out.println(ans.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}