#### [OK] 1.rb
```ruby
require "json"

def convert_to_json(obj)
  obj.to_json
end

p convert_to_json(1)   # => "1"
p convert_to_json("x") # => "\"x\""
```

```console
% ruby 1.rb
"1"
"\"x\""

% crystal 1.rb
"1"
"\"x\""
```