Language: C++

//#include <bits/stdc++.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cstring>
#include <deque>
#include <map>
using namespace std;

#define ii pair <int, int>
#define lli long long
#define pb push_back
#define X first
#define Y second

const int Mod = 1E9 + 7;
const int Inf = 1E9 + 7;
const int N = 2E5 + 10;

long long n, a[N], res = 0;

void Input()
{
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
}

void Solve()
{
    for (int i = 2; i <= n; i++) {
        res += max(a[i - 1] - a[i], 0);
        a[i] = max(a[i], a[i - 1]);
    }

    cout << res;
}

#define task "test"
int main()
{
    if (fopen(task ".inp", "r")) {
        freopen(task ".inp", "r", stdin);
        freopen(task ".out", "w", stdout);
    }
    int testcase = 1;
    /// cin >> testcase;
    while (testcase--) {
        Input();
        Solve();
    }
}




Compiler output:
a.cc: In function 'void Solve()':
a.cc:32:19: error: no matching function for call to 'max(long long int, int)'
   32 |         res += max(a[i - 1] - a[i], 0);
      |                ~~~^~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:32:19: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   32 |         res += max(a[i - 1] - a[i], 0);
      |                ~~~^~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:32:19: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   32 |         res += max(a[i - 1] - a[i], 0);
      |                ~~~^~~~~~~~~~~~~~~~~~~~