package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
)

var modVar = int64(1e9) + int64(7)

func solve(in io.Reader, out, err io.Writer) {
	num, size, count, total := 0, int64(0), int64(0), int64(0)
	fmt.Fscan(in, &num)

	for i := 0; i < num; i++ {
		fmt.Fscan(in, &size, &count)
		size = (size + 1) / 2
		total = (total + (size % modVar * (count % modVar))) % modVar
	}
	fmt.Fprintln(out,total)
}

func main() {
	br := bufio.NewReaderSize(os.Stdin, int(1e7))
	solve(br, os.Stdout, os.Stderr)
}