Problem statement here
My approach gives wrong ans in the fourth test case 
.
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
vector<vector<ll>>adj;
vector<ll>level;
const ll lg = 21;
const ll size = 1e5 + 2;
ll up[300005][21];
ll dfs(ll child, ll parent)
{
up[child][0] = parent;
for(int i=1; i<lg; i++)
{
up[child][i] = up[up[child][i-1]][i-1];
}
for(auto i:adj[child])
{
if(i != parent)
{
level[i] = level[child] + 1;
dfs(i,child);
}
}
}
ll lift(ll x, ll y)
{
for(int i=0; i<lg; i++)
{
if(1<<i & y)
{
x = up[x][i];
y -= 1<<i;
}
}
return x;
}
ll lca(ll a, ll b)
{
if(level[a] > level[b])
swap(a,b);
ll d = level[b] - level[a];
while(d > 0)
{
ll i = log2l(d);
b = up[b][i];
d -= (1<<i);
}
if( a == b)
return a;
for(int i=20; i>=0; i--)
{
if(up[a][i] !=0 && (up[a][i] != up[b][i]))
{
a = up[a][i] , b = up[b][i];
}
}
return up[a][0];
}
pair<ll,ll> distance(ll a, ll b)
{
ll ancestor = lca(a,b);
return {level[a] + level[b] - 2*level[ancestor], ancestor};
}
ll solve()
{
ll n;
cin>>n;
adj.clear();
adj.resize(n+4);
level.clear();
level.resize(n+4);
for(int i=2; i<=n; i++)
{
ll u,v;
cin>>u>>v;
//v = i;
adj[u].push_back(v);
adj[v].push_back(u);
}
dfs(1,0);
ll q;
cin>>q;
while(q--)
{
ll a,b,c;
cin>>a>>b>>c;
auto ab = distance(a,b);
if(ab.first <=c)
{
cout<<b<<"\n";
continue;
}
ll aa = level[a] - level[ab.second];
if(aa >= c)
{
cout<<lift(a,aa)<<"\n";
}
else
{
cout<<lift(b,(ab.first - c))<<"\n";
}
}
return 1;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll ignore = 1;
//cin>>ignore;
while(ignore--)
{
solve();
}
}