let lagrange (x:float list) (y:float list) (v:float) =
    [for i in 0..x.Length - 1 ->
         [for j in [0..i-1]@[i+1..x.Length - 1] ->
            (v - x.[j]) / (x.[i] - x.[j])]
         |> List.fold (*) y.[i]]
    |> List.sum

//Usage

//x values
let x = [111.0;112.0;113.0;114.0;115.0]
//y values
let y = [13.0;24.0;35.0;46.0;57.0]
//interpolating value
let v = 117.0

lagrange x y v