# Project Euler #015

Starting in the top left corner of a 2 × 2 grid, there are 6 routes (without backtracking) to the bottom right corner.

How many routes are there through a 20 × 20 grid?

```
let rec find_path square_size x y =
let complete = x = square_size || y = square_size
match complete with
| true -> 1L
| false -> (find_path square_size (x + 1) y) + find_path square_size x (y + 1)
// This will take some time
find_path 20 0 0
```

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