package main

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

func main() {
    N := InputInt()
    var c, d, a int
    mod := int(math.Pow(10, 9)) + 7
    for i := 0; i < N; i++ {
        s := strings.Split(Input(), " ")
        c = ToInt(s[0])
        d = ToInt(s[1])
        a += ((c / 2 + c % 2) * d) % mod
    }
    Print(a % mod)
}

func Print(x ...interface{}){
    l := len(x) - 1
    for ii, vi := range x {
        fmt.Print(vi)
        if ii == l {
            fmt.Print("\n")
        } else {
            fmt.Print(" ")
        }
    }
}
var sc = bufio.NewScanner(os.Stdin)
func Input() string {
    sc.Scan()
    return sc.Text()
}
func InputInt() int {
    sc.Scan()
    i, e := strconv.Atoi(sc.Text())
    if e != nil {panic(e)}
    return i
}
func BinCount(x int) int {
    s := fmt.Sprintf("%b", x)
    c := 0
    for _, i := range s {
        if i == '1' {c += 1}
    }
    return c
}
func ToInt(x string) int {
    i, e := strconv.Atoi(x)
    if e != nil {panic(e)}
    return i
}