Cosa trocoloca

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
using namespace std;
vector<vector< int > > Ary;
long long An[100001][18], Dis[100001][18], P[100001], DPK[100001], DP2[19];
long long Query(int a,int b)
{
    if(a == b)
        return 0;
    long long r = 0;
    if(P[a]!=P[b])
    {
        if(P[a] > P[b])
            swap(a,b);
        long long k = DPK[b], d = P[b] - P[a];
        while(d)
        {
      //      cout<<k<<" "<<d<<"  "<<DP2[k]<<" "<<r<<"  "<<Dis[b][k]<<endl;

            if(DP2[k] <= d)
            {
                d -= DP2[k];
                r += Dis[b][k];
                b = An[b][k];
            }
            k--;
        }
    }
    int k = DPK[P[a]];
    //cout<<r<<"---"<<a<<"  "<<b<<endl;
    if(a == b)
        return r;
    while(k>=0)
    {
        //cout<<a<<"  "<<b<<"  "<<An[a][k]<<"  "<<An[b][k]<<" | | "<<r<<" - "<<k<<endl;
        if(An[a][k]!=An[b][k])
        {
            r += Dis[a][k] + Dis[b][k];
            a = An[a][k], b = An[b][k];
        }
        k--;
    }
    r+= Dis[a][0] + Dis[b][0];
    return r;
}
void DFS(int n,int d)
{
    P[n] = d;
    for(int i = 1;i<18;i++)
    {
        An[n][i] = An[An[n][i-1]][i-1];
        Dis[n][i] = Dis[An[n][i-1]][i-1] + Dis[n][i-1];
    }
    for(auto k : Ary[n])
        DFS(k,d+1);
}
void Caso(int N)
{
    Ary.clear();
    Ary.resize(N,vector<int> (0));
    memset(An,0,sizeof(An));
    memset(Dis,0,sizeof(Dis));
    memset(P,0,sizeof(P));
    for(int i = 1;i<N;i++)
    {
        int a,l;
        scanf("%d %d",&a,&l);
       // cout<<"Leido un nodo -------------"<<endl;
        An[i][0] = a, Dis[i][0] = l;
        Ary[a].push_back(i);
    }
    DFS(0,0);
    int Q;
    scanf("%d",&Q);
    for(int i = 0;i<Q;i++)
    {
        int a,b;
        scanf("%d %d",&a,&b);
        printf("%lld",Query(a,b));
        if(i<Q-1)
            printf(" ")
    }
    //printf("\n");
}
int main()
{
    memset(DP2,0,sizeof(DP2)), memset(DPK,0,sizeof(DPK));
    for(int i = 1, k = 0;i<100000;i*=2,k++)
    {
        DPK[i] = 1;
        DP2[k] = i;
    }

    for(int i = 1;i<100000;i++)
        DPK[i]+=DPK[i-1];
    int n;
    scanf("%d",&n);
    while(n)
    {
        //cout<<"--------"<<endl;
        Caso(n);
        //cout<<"--------"<<endl;
        scanf("%d",&n);
        if(n)
            printf("\n");
    }
}
/*
6
0 8
1 7
1 9
0 3
4 2
4
2 3
5 2
1 4
0 3
2
0 1
2
1 0
0 1
6
0 1000000000
1 1000000000
2 1000000000
3 1000000000
4 1000000000
15
5 0
4 0
3 0
2 0
1 0
5 1
4 1
3 1
2 1
5 2
4 2
3 2
5 3
4 3
5 4
*/