We are given a sequence of coplanar points and see all the possible triangles that may be generated which all combinations of three points.

We have the following list of points with the cartesian coordinates of each one:
```
Points [x, y]
   A   [1, 2]
   B   [3, 3]
   C   [4, 1]
   D   [1, 1]
   E   [4, -1]
```
With these points we may have the following triangles: ```ABC, ABD, ABE, ACD, ACE, ADE, BCD, BCE, BDE, CDE.``` There are three special ones: ```ABC, ACD and CDE```, that have an angle of 90°. All is shown in the picture below:



We need to count all the rectangle triangles that may be formed by a given list of points.

The case decribed above will be:
```python
count_rect_triang([[1, 2],[3, 3],[4, 1],[1, 1],[4, -1]]) == 3
```

Observe this case:
```python
count_rect_triang([[1, 2],[4, -1],[3, 3],[4, -1],[4, 1],[1, 1],[4, -1], [4, -1], [3, 3], [1, 2]]) == 3
```
If no rectangle triangles may be generated the function will output ```0```.

Enjoy it!

```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 = 'from itertools import combinations\ndef count_rect_triang(points):\n    n=0\n    points_set=set()\n    for p in points:\n        points_set.add(tuple(p))\n    for (x1,y1),(x2,y2),(x3,y3) in combinations(points_set,3):\n        l1,l2,l3=sorted([(x2-x1)**2+(y2-y1)**2,(x3-x2)**2+(y3-y2)**2,(x1-x3)**2+(y1-y3)**2])\n        if l1+l2==l3:\n            n+=1\n    return n'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'count_rect_triang'
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: 6562