euler20

euler20.fsx

let units bi = (bi % 10I, bi/10I)

let rec sum bi = match units(bi) with
                 | (u, r) when r = 0I -> u
                 | (u, r) -> u + sum(r)
                       
let rec fac(n:int): bigint = match n with  
                             | 1 -> bigint(1)  
                             | n -> bigint(n) * fac(n - 1) 
                       
let result = sum(fac(100))

printfn "%A" result