#include <bits/stdc++.h>
#define ll long long
#define inf (ll)(1e15)
#define mod (ll)1e9+7
#define dbg(x) cerr <<#x << ' ' << x <<endl;
using namespace std;
void printvec(vector<ll>& v)
{
for (auto &&i : v)
{
cout <<i<<' ';
}
cout << endl;
}
vector<pair<ll,ll>> dp;
map<pair<ll,ll>,ll> wt;
vector<vector<ll>> adj;
vector<ll> parr;
vector<ll> diameter;
void dfs(ll node, ll par)
{
parr[node]=par;
ll mx1=0;
ll mx2=0;
ll mxd=0;
for (auto &&e : adj[node])
{
if(e==par)continue;
dfs(e,node);
ll v=wt[{node,e}]+dp[e].second;
mxd=max(mxd,diameter[e]);
if(v > mx2)
{
mx2=v;
if(mx2>mx1) swap(mx1,mx2);
}
}
dp[node]={mx1+mx2,mx1};
diameter[node]=max(mxd,dp[node].first);
}
void tl3(ll node)
{
if(node==0) return;
ll mx1=0;
ll mx2=0;
ll mxd=0;
for (auto &&e : adj[node])
{
if(e==parr[node]) continue;
ll v=wt[{node,e}]+dp[e].second;
mxd=max(mxd,diameter[e]);
if(v > mx2)
{
mx2=v;
if(mx2>mx1) swap(mx1,mx2);
}
}
dp[node]={mx1+mx2,mx1};
diameter[node]=max(mxd,dp[node].first);
tl3(parr[node]);
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
ll n,q,w;
cin>>n>>q>>w;
vector<pair<ll,ll>> edges(n-1);
adj.resize(n);
dp.resize(n);
parr.resize(n);
diameter.resize(n);
for (int i=0;i<n-1;i++)
{
ll c;
cin>>edges[i].first>>edges[i].second>>c;
edges[i].first--;
edges[i].second--;
adj[edges[i].first].push_back(edges[i].second);
adj[edges[i].second].push_back(edges[i].first);
ll u=edges[i].first;
ll v=edges[i].second;
wt[{u,v}]=c;
wt[{v,u}]=c;
}
dfs(0,0);
ll last=0;
while(q--)
{
ll d,e;
cin>>d>>e;
d=(d+last)%(n-1);
e=(e+last)%w;
wt[edges[d]]=e;
wt[{edges[d].second,edges[d].first}]=e;
ll nd=edges[d].second;
if(edges[d].second == parr[edges[d].first]) nd=edges[d].first;
tl3(nd);
cout << diameter[0] << endl;
last=diameter[0];
}
}
