open System

let abx = stdin.ReadLine().Split() |> Array.map int |> Array.map float
let [|a;b;x|] = abx


let harf = a * a * b / 2.0
let pat = if x < harf then 1 else 2

let tate1 = (x * 2.0) / (a * b)
let tate2 = ((a * a * b - x) * 2.0) / (a * a)

let rad1 = Math.Atan (tate1 / b)
let rad2 = Math.Atan (tate2 / a)

let f rad = rad * 180.0 / Math.PI

let ans = if (pat = 1) then (90.0 - (f rad1)) else (f rad2)

ans
|>stdout.WriteLine