In this Kata, you will be given a number `n` (`n > 0`) and your task will be to return the smallest square number `N` (`N > 0`) such that `n + N` is also a perfect square. If there is no answer, return `-1` (`nil` in Clojure, `Nothing` in Haskell, `None` in Rust). 

```clojure 
solve 13 = 36
; because 36 is the smallest perfect square that can be added to 13 to form a perfect square => 13 + 36 = 49

solve 3 = 1 ; 3 + 1 = 4, a perfect square
solve 12 = 4 ; 12 + 4 = 16, a perfect square
solve 9 = 16 
solve 4 = nil
```

```csharp 
solve(13) = 36
//because 36 is the smallest perfect square that can be added to 13 to form a perfect square => 13 + 36 = 49

solve(3) = 1 // 3 + 1 = 4, a perfect square
solve(12) = 4 // 12 + 4 = 16, a perfect square
solve(9) = 16 
solve(4) = -1
```

```haskell 
solve 13 = Just 36
-- because 36 is the smallest perfect square that can be added to 13 to form a perfect square => 13 + 36 = 49

solve 3 = Just 1 -- 3 + 1 = 4, a perfect square
solve 12 = Just 4 -- 12 + 4 = 16, a perfect square
solve 9 = Just 16 
solve 4 = Nothing
```

```python
solve(13) = 36
# because 36 is the smallest perfect square that can be added to 13 to form a perfect square => 13 + 36 = 49

solve(3) = 1 # 3 + 1 = 4, a perfect square
solve(12) = 4 # 12 + 4 = 16, a perfect square
solve(9) = 16 
solve(4) = -1
```

More examples in test cases. 

Good luck!

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

def _disabled_input(*args, **kwargs):
    raise RuntimeError("input() is disabled in callable mode")
builtins.input = _disabled_input

ns = {"__name__": "__judge__"}  # prevent if __name__ == "__main__" blocks
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'def solve(n): \n    X = 1e9\n    for i in range(1, int(n**(1/2)) + 1): \n        if n % i == 0: \n            a = i \n            b = n // i    \n            if b - a != 0 and (b - a) % 2 == 0: \n                 X = min(X, (b - a) // 2) \n    return(X * X if X != 1e9 else -1) '
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'solve'
if _fn_name:
    if "Solution" in ns:
        try:
            _obj = ns["Solution"]()
            if hasattr(_obj, _fn_name):
                _target = getattr(_obj, _fn_name)
        except Exception:
            _target = None
    if _target is None and _fn_name in ns and callable(ns[_fn_name]):
        _target = ns[_fn_name]
# Fallback: if there's exactly one user-defined function, use it
if _target is None:
    _cands = [v for k, v in ns.items() if callable(v) and getattr(v, "__module__", "") in ("__judge__", "__main__")]
    _user_funcs = [c for c in _cands if getattr(c, "__name__", "").startswith("_") is False]
    if len(_user_funcs) == 1:
        _target = _user_funcs[0]
if _target is None:
    raise RuntimeError(f"Could not resolve callable '{_fn_name}'")

_raw = sys.stdin.read().strip()
if _raw:
    _parsed = json.loads(_raw)
    if isinstance(_parsed, dict):
        _kwargs = _parsed.get("kwargs", {})
        _args = _parsed.get("args", [])
    else:
        _args, _kwargs = _parsed, {}
else:
    _args, _kwargs = [], {}
if not isinstance(_args, (list, tuple)):
    _args = [_args]
_res = _target(*_args, **_kwargs)
try:
    sys.stdout.write(repr(_res) + "\n")
except Exception:
    pass

```

Measured memory_bytes: 5510