Some people will make friend requests. The list of their ages is given and ages[i] is the age of the ith person. 
Person A will NOT friend request person B (B != A) if any of the following conditions are true:

age[B] <= 0.5 * age[A] + 7
age[B] > age[A]
age[B] > 100 && age[A] < 100

Otherwise, A will friend request B.
Note that if A requests B, B does not necessarily request A.  Also, people will not friend request themselves.
How many total friend requests are made?
Example 1:
Input: [16,16]
Output: 2
Explanation: 2 people friend request each other.

Example 2:
Input: [16,17,18]
Output: 2
Explanation: Friend requests are made 17 -> 16, 18 -> 17.
Example 3:
Input: [20,30,100,110,120]
Output: 3
Explanation: Friend requests are made 110 -> 100, 120 -> 110, 120 -> 100.

 
Notes:

1 <= ages.length <= 20000.
1 <= ages[i] <= 120.

```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 = 'class Solution:\n    def numFriendRequests(self, ages: List[int]) -> int:\n        if ages == []:\n            return 0\n        ages.sort()\n        res = 0\n        for i in range(len(ages) - 1, -1, -1):\n            if ages[i] < 15:\n                break\n            age = ages[i]\n            left = self.binary_search_left(ages, 0, i, age // 2 + 8)\n            right = self.binary_search_right(ages, i, len(ages) - 1, age)\n            #print(left, right)\n            res += max(0, right - left)\n        return res\n\n    def binary_search_left(self, ages, start, end, target):\n        while start + 1 < end:\n            mid = (start + end) // 2\n            if ages[mid] < target:\n                start = mid\n            else:\n                end = mid\n        \n        if ages[start] >= target:\n            return start\n        if ages[end] >= target:\n            return end\n        return -1\n\n    def binary_search_right(self, ages, start, end, target):\n        while start + 1 < end:\n            mid = (start + end) // 2\n            if ages[mid] <= target:\n                start = mid\n            else:\n                end = mid\n        if ages[end] <= target:\n            return end\n        if ages[start] <= target:\n            return start\n        return -1'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'numFriendRequests'
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: 5922