let MOD = pown 10 9 |> (+)7 |> int64
let (|ODD|EVE|) x = if x%2L=0L then EVE else ODD

let R() = stdin.ReadLine()

let solve cs ds =
    let rec f score cs ds =
        match cs, ds with
        | [], _ | _, [] -> score
        | c::cs, d::ds ->
            match c with
            | EVE -> f ((score+(c%MOD/2L)*d%MOD)%MOD) cs ds
            | ODD -> f ((score+(c%MOD/2L+1L)*d%MOD)%MOD) cs ds 
    f 0L cs ds
    
let N = R() |> int
let C, D =
    let t = List.init N (fun _ ->
        let t = R().Split()
        int64 t.[0], int64 t.[1])
    let c = t |> List.map fst
    let d = t |> List.map snd
    c, d
       
solve C D
|> stdout.WriteLine