import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Iterator;


public class Main_yukicoder146 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        final int MOD = 1000000007;
        int n = sc.nextInt();
        long ret = 0;
        for (int i = 0; i < n ; i++) {
        	long c = sc.nextLong();
        	long d = sc.nextLong() % MOD;
        	long tmp = (c / 2 + c % 2) % MOD;
        	tmp = tmp * d % MOD;
        	ret = (ret + tmp) % MOD;
        }

        System.out.println(ret);

        pr.close();
        sc.close();
    }

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;
		
		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}
		
		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}
		
		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}