Language: C++

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
#include <map>
#include <queue>

long long dfs(long long depth, long long p, std::vector<long long> v) {
    long long max_depth = 0;
    for (int i = 0; i < v.size(); i++) {
        if (v[i] == p) {
            max_depth = std::max(max_depth, dfs(depth + 1, i + 2, v));
        }
    }
    max_depth = std::max(max_depth, std::count(v.begin(), v.end(), p) + depth);
    return max_depth;
}

int main() {
    long long n;

    std::cin >> n;

    std::vector<long long> v(n - 1);
    for (int i = 0; i < n - 1; i++) {
        std::cin >> v[i];
    }

    long long max = 0;
    for (int i = 0; i < n; i++) {
        max = std::max(max, std::count(v.begin(), v.end(), i + 1));
    }
    max = std::max(max, dfs(0, 1, v));

    std::cout << max << std::endl;

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:32:23: error: no matching function for call to 'max(long long int&, std::__iterator_traits<__gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >, void>::difference_type)'
   32 |         max = std::max(max, std::count(v.begin(), v.end(), i + 1));
      |               ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:1:
/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:32:23: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'std::__iterator_traits<__gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >, void>::difference_type' {aka 'long int'})
   32 |         max = std::max(max, std::count(v.begin(), v.end(), i + 1));
      |               ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/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:4:
/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:32:23: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   32 |         max = std::max(max, std::count(v.begin(), v.end(), i + 1));
      |               ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~