[boost] Meta-math

I was just playing around, trying to compute a square root at compile time. I came up with the following: template < unsigned int N, unsigned int X = 1, unsigned int X2 = ( X + N / X ) / 2 > struct Sqrt { typedef typename Sqrt < N, X2 > :: ValueHolder ValueHolder; }; template < unsigned int N, unsigned int X > struct Sqrt < N, X, X > { struct ValueHolder { enum ValueStorage { Value = X }; }; }; This works for most values, but unfortunately some ( like 80 ) end up oscillating and X never becomes equal to X2. How could I go about correcting this? -Jason