package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

// 10^9 + 7
const P = 1000000007

var sc = bufio.NewScanner(os.Stdin)

func next() string {
	sc.Split(bufio.ScanWords)
	if !sc.Scan() {
		panic("could not scan a word from the reader")
	}
	return sc.Text()
}

func nextInt() int {
	i, e := strconv.Atoi(next())
	if e != nil {
		panic(e)
	}
	return i
}

func nextLong() int64 {
	i, e := strconv.ParseInt(next(), 10, 64)
	if e != nil {
		panic(e)
	}
	return i
}

func nextLine() string {
	sc.Split(bufio.ScanLines)
	if !sc.Scan() {
		panic("could not scan a line from the reader")
	}
	return sc.Text()
}

func main() {
	N := nextInt()
	var res int64
	for i := 0; i < N; i++ {
		C, D := nextLong(), nextLong()
		res += ((C/2 + C%2) % P) * (D % P)
		res %= P
	}
	fmt.Println(res)
}