#include "september.h"
#include <bits/stdc++.h>
using namespace std;
const int NM = 1e5;
int N, M;
vector <int> son[NM+5];
int timer, tin[NM+5], tout[NM+5];
int sum[NM+5], res[NM+5];
void dfs(int u){
tin[u] = ++timer;
for (int v : son[u]) dfs(v);
tout[u] = timer;
}
bool is_ancestor(int u, int v){
return tin[u] <= tin[v] && tout[u] >= tout[v];
}
int solve(int _N, int _M, vector <int> F, vector <vector <int> > S){
N = _N, M = _M;
for (int i = 0; i < N; i++) son[i].clear();
for (int i = 1; i < N; i++){
int p = F[i];
son[p].push_back(i);
}
timer = 0;
dfs(0);
for (int i = 0; i < M; i++){
for (int j = 0; j < N; j++) sum[j] = 0;
for (int j = 0; j < N-1; j++)
for (int k = j+1; k < N-1; k++)
if (is_ancestor(S[i][j], S[i][k]) || (i > 0 && res[S[i][j]] >= res[S[i][k]])) sum[j]++, sum[k]--;
res[S[i][0]] = 1;
for (int j = 0; j+1 < N-1; j++){
if (j > 0) sum[j] += sum[j-1];
if (sum[j] > 0) res[S[i][j+1]] = res[S[i][j]];
else res[S[i][j+1]] = res[S[i][j]]+1;
}
}
int mx = 0;
for (int i = 1; i < N; i++) mx = max(mx, res[i]);
return mx;
}
