Language: C++

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using u32 = uint32_t;
using vi = vector<int>;    using vvi = vector<vi>;
using vb = vector<bool>;   using vvb = vector<vb>;
using vl = vector<ll>;     using vvl = vector<vl>;
using vd = vector<double>; using vvd = vector<vd>;

#define MAXC(c, x) (c = max(c, x))
#define MINC(c, x) (c = min(c, x))

#define REP(i,n) for(auto i = 0 * (n), i##_len = (n); i < i##_len; ++i)
#define ALL(c) (c).begin(), (c).end()
#define FOR(i,s,n) for(ll i=s, i##_len=(ll)(n); i<i##_len; ++i)
#define TEN(x) ((ll)1e##x)
const ll mod = TEN(9) + 7;

int main() {
#ifdef INPUT_FROM_FILE
	ifstream cin("sample.in");
	ofstream cout("sample.out");
#endif
	cin.tie(0);
	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(50);
	ll n; cin >> n;
	vvl path(n);
	REP(i, n - 1) {
		ll a; cin >> a;
		path[a - 1].push_back(i + 1);
	}
	function<ll(ll)> dfs = [&](ll cur) {
		vl a;
		for (auto&& x : path[cur]) {
			a.push_back(dfs(x));
		}
		sort(ALL(a));
		reverse(ALL(a));

		ll ans = 0;
		REP(i, a.size()) {
			ans = max(ans, a[i] + i + 1);
		}
		return ans;
	};
	cout << dfs(0) << endl;


	return 0;
}

Compiler output:
a.cc: In lambda function:
a.cc:44:34: error: no matching function for call to 'max(ll&, long long unsigned int)'
   44 |                         ans = max(ans, a[i] + i + 1);
      |                               ~~~^~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 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:44:34: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'long long unsigned int')
   44 |                         ans = max(ans, a[i] + 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:
/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:44:34: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   44 |                         ans = max(ans, a[i] + i + 1);
      |                               ~~~^~~~~~~~~~~~~~~~~~~