nthr(n,r) <= n^(1/r)

nthroot(n,r)=
  a = n/r
  g = n
  > g!=a
    g = a
    a = (1/r)*(((r-1)*g)+(n/(g^(r-1))))
  <
  <= a
.

#.output(nthr(2,2))
#.output(nthroot(2,2))