open System
open FSharp.Collections

let secondsToArrive  (distance:int) (speed:int)  =
    ((float distance)/((float speed)*1000.0))*3600.0

let checkGreenLight (duration:int) (arrive:float)  =
    let period=(arrive/(float duration))
    let intperiod= int( System.Math.Round(period,10))
    (intperiod % 2) = 0

let mutable SuccesChekers = []
let addToList (listan) (element) = element::listan
let speed = int(Console.In.ReadLine())
let lightCount = int(Console.In.ReadLine())



for i in 0 .. lightCount - 1 do
    let token = (Console.In.ReadLine()).Split [|' '|]
    let distance = int(token.[0])
    let duration = int(token.[1])
    let currentSeconds = secondsToArrive distance
    let currentGreen =  checkGreenLight duration
    let succesCheck = currentSeconds >>  currentGreen
    SuccesChekers <- addToList SuccesChekers succesCheck
    ()
let mutable maxSpeed =0
let checkGivenSpeed speed (listOfChecks: (int->bool)list) =
    List.forall(fun elem-> elem speed ) listOfChecks

let speeds= Seq.sortDescending (seq { 0 .. speed })

let result=Seq.find (fun elem-> (eprintfn "%i" elem );  checkGivenSpeed elem SuccesChekers) speeds



(* Write an action using printfn *)
(* To debug: eprintfn "Debug message" *)

printfn "%i" result