Consider the following array:

```
[1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891011...]
```

If we join these blocks of numbers, we come up with an infinite sequence which starts with `112123123412345123456...`. The list is infinite.

You will be given an number (`n`) and your task will be to return the element at that index in the sequence, where `1 ≤ n ≤ 10^18`. Assume the indexes start with `1`, not `0`.  For example:

```
solve(1) = 1, because the first character in the sequence is 1. There is no index 0. 
solve(2) = 1, because the second character is also 1.
solve(3) = 2, because the third character is 2.
```

More examples in the 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 = 'from math import sqrt, ceil, log10\nimport numpy as np\n\ndef getGreatest(n, d, prefix):\n    rows = 9 * 10**(d - 1)\n    triangle = rows * (d + rows * d) // 2\n    l = 0\n    r = triangle\n \n    while l < r:\n        mid = l + ((r - l) >> 1)\n        triangle = mid * prefix + mid * (d + mid * d) // 2\n        prevTriangle = (mid-1) * prefix + (mid-1) * (d + (mid-1) * d) // 2\n        nextTriangle = (mid+1) * prefix + (mid+1) * (d + (mid+1) * d) // 2\n \n        if triangle >= n:\n            if prevTriangle < n:\n                return prevTriangle\n            else:\n                r = mid - 1\n        else:\n            if nextTriangle >= n:\n                return triangle\n            else:\n                l = mid\n    return l * prefix + l * (d + l * d) // 2\n\ndef findDiff(n, x):\n    mult = 1\n    temp=x/10\n    while temp >= 1:\n        temp /= 10\n        mult *= 10\n    d = round(log10(mult))+1\n    prefixes = 0\n    for z in range(1,d):\n        prefixes += (9*z*10**(z-1))\n    n -= calcSeq(mult-1)\n    return n-getGreatest(n, d, prefixes)\n        \ndef calcSeq(current):\n    x = np.int64(current*(current+1)/2)\n    mult = 10\n    temp=np.int64(current)\n    while temp > 0:\n        temp=current\n        temp -= mult-1\n        mult *= 10\n        if temp> 0: x += np.int64(temp*(temp+1)/2)\n    return x\n            \ndef solve(n): \n    maxN = n\n    minN = 0\n    x = float(0)\n    delta=2\n    prev = 0\n    current = round(sqrt(2*n))\n    prevRight = True\n    while maxN-minN>1:\n        x = calcSeq(current)\n        delta = abs(current-prev)\n        prev = current\n        if x < n and prevRight:\n            current += ceil((maxN-current)/2)\n            prevRight = True\n        elif x < n:\n            minN = current\n            current += ceil((maxN-current)/2)\n            prevRight = True\n        elif x > n and prevRight == False:\n            maxN = current\n            current -= round((current-minN)/2)\n            prevRight = False\n        elif x > n:\n            current -= round((current-minN)/2)\n            prevRight = False\n        else: \n            maxN = current\n            minN = current-1\n    if calcSeq(current) < n: \n        current+=1\n    prev = current-1\n    \n    element = findDiff(n,prev)\n    nDigits, nines = 1, 9\n    total = float(nDigits*nines)\n    while total < element:\n        nDigits += 1\n        nines *= 10\n        total += nDigits*nines \n    total -= nDigits*nines\n    element2 = element-total\n    start = 10**(nDigits-1)\n    number = str(start + ceil(element2/nDigits) - 1)\n    \n    return int(number[(int(element2)-1)%nDigits])'
_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: 7190