Given an array of positive integers target and an array initial of same size with all zeros.
Return the minimum number of operations to form a target array from initial if you are allowed to do the following operation:

Choose any subarray from initial and increment each value by one.

The answer is guaranteed to fit within the range of a 32-bit signed integer.
 
Example 1:
Input: target = [1,2,3,2,1]
Output: 3
Explanation: We need at least 3 operations to form the target array from the initial array.
[0,0,0,0,0] increment 1 from index 0 to 4 (inclusive).
[1,1,1,1,1] increment 1 from index 1 to 3 (inclusive).
[1,2,2,2,1] increment 1 at index 2.
[1,2,3,2,1] target array is formed.

Example 2:
Input: target = [3,1,1,2]
Output: 4
Explanation: (initial)[0,0,0,0] -> [1,1,1,1] -> [1,1,1,2] -> [2,1,1,2] -> [3,1,1,2] (target).

Example 3:
Input: target = [3,1,5,4,2]
Output: 7
Explanation: (initial)[0,0,0,0,0] -> [1,1,1,1,1] -> [2,1,1,1,1] -> [3,1,1,1,1] 
                                  -> [3,1,2,2,2] -> [3,1,3,3,2] -> [3,1,4,4,2] -> [3,1,5,4,2] (target).

Example 4:
Input: target = [1,1,1,1]
Output: 1

 
Constraints:

1 <= target.length <= 10^5
1 <= target[i] <= 10^5

```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    #Version 1: DFS with memoization\n    #Brute force\n    #TC: O(n^3), SC: O(n^2)\n    '''\n    def minNumberOperations(self, target: List[int]) -> int:\n        \n        def get(num, dp):\n            if not num:\n                return 0\n            numt = tuple(num)\n            if numt not in dp:\n                val = min(num)\n                left = 0\n                result = val\n                for k in range(len(num)):\n                    num[k] -= val\n                    if num[k] == 0:\n                        if left < k:\n                            result += get(num[left:k], dp)\n                        left = k + 1\n                if left < len(num):\n                    result += get(num[left:], dp)\n                dp[numt] = result\n            return dp[numt]\n        \n        dp = {}\n        return get(target, dp)\n    '''\n    \n    #Version 2: Use stack to check the increment status\n    #If the number is smaller than the top of the stack, it means some increments used on the top of the stack will not be used for the new number.\n    #Therefore, we can pop the stack.\n    #TC: O(n), SC: O(n)\n    def minNumberOperations(self, target: List[int]) -> int:\n        ans = 0\n        stack = [0]\n        for k in target:\n            while len(stack) >= 1 and stack[-1] >= k:\n                ans += (stack[-1]-max(k, stack[-2]))\n                stack.pop()\n            stack.append(k)\n        #print(stack)\n        return ans + stack[-1]\n    \n    '''\n    def minNumberOperations(self, target: List[int]) -> int:\n        ans = 0\n        current = 0\n        for k in target:\n            if k > current:\n                ans += (k-current)\n            current = k\n        return ans\n    '''            "
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'minNumberOperations'
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: 5578