import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.stream.Stream;

import static java.lang.System.in;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        long typeOfDesk = Long.parseLong(reader.readLine());
        long accomodates = 0;
        for (long desk = 0; desk < typeOfDesk; desk++) {

            String[] inputs = reader.readLine().split(" ");
            long c = Long.parseLong(inputs[0]) % (100000007);
            long d = Long.parseLong(inputs[1]) % (100000007);
            accomodates += ((c + 2 - 1) / 2) * d % (100000007);

        }
        System.out.println(accomodates);
    }
}