#include <stdio.h>
#include <assert.h>
#include <vector>
#include <iostream>
#define MAXN 1000000

int maxResult = 0;
using namespace std;
vector<int> arr;

void calculateAt(int i, const int MAXf, const char Q[], const int A[])
{

    if(i >= MAXf)
        return;
    else
    {
        if(arr[i] == -1)
        {

            if(arr[A[i]] == -1)
               calculateAt(A[i], MAXf, Q, A);

            arr[i] = arr[A[i]] + (Q[i] == 'P' ? 1 : (Q[i] == 'N' ? 2 : 3));

            if(arr[i] > maxResult)
                maxResult = arr[i];

        }
        calculateAt(i+1, MAXf, Q, A);
    }
}

int falsifica(int N, char Q[], int A[]) {
    // Mettete qui il codice della soluzione

//    calculateAt(1, N, Q, A);

    vector<int> coda;

    int i = 1;

    coda.push_back(0);

    while(i < N)
    {
        if(arr[i] == -1)
        {

            if(arr[A[i]] == -1)
            {
                    i = A[i];
                    coda.push_back(i);
                    continue;
            }
            //   calculateAt(A[i], MAXf, Q, A);

            arr[i] = arr[A[i]] + (Q[i] == 'P' ? 1 : (Q[i] == 'N' ? 2 : 3));

            if(arr[i] > maxResult)
                maxResult = arr[i];

        }

       // if(coda.size() > 0)
         //   coda.erase(coda.size()-1);
         if(coda.size() > 1)
         {
         coda.erase(coda.begin() + coda.size()-1);
         i = coda[coda.size()-1] -1;

         }

         if(coda.size() == 1)
         {
            i++;
            coda[0] = i;
            }
    }


    return maxResult;
}


char Q[MAXN];
int  A[MAXN];

int main() {
    int N, i;

    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    cin >> N;
    Q[0] = 'X';
    A[0] = -1;
    arr.push_back(0);
    for(i=1; i<N; i++) {
            cin >> Q[i];
            cin >> A[i];
       // assert(1 == fscanf(fr, " %c", &Q[i]));
       // assert(1 == fscanf(fr, "%d", &A[i]));
        arr.push_back(-1);
    }

    cout <<  falsifica(N, Q, A);

    return 0;
}