### The Problem

Compute 2^{1000} and sum its digits.

### The Solution

Like Problem 13, this problem is
trivially easy because of .NET's `BigInteger`

data type.

```
(pown 2I 1000).ToString()
|> Seq.map (fun c -> int32(c) - int32('0'))
|> Seq.sum
```

The `pown`

function returns 2^{1000} as a `BigInteger`

. (Suffixing a numeric literal
with `I`

means it is a `BigInteger`

literal)

Strings can be treated as `Seq<char>`

and that's what we do here. We convert each digit into
an integer and then finally sum the result.