#include <bits/stdc++.h>
using namespace std;
vector<pair<long long,long long>> adj[100001];
long long dist[5001];
void dfs(long long i,long long d)
{
dist[i]=d;
for(auto it : adj[i])
{
long long br=it.first;
long long br2=it.second;
if(dist[br]==-1)
dfs(it.first,d+br2);
}
}
int main()
{
ios::sync_with_stdio((false));
cin.tie(NULL);
cout.tie(NULL);
long long n,q,w;
cin>>n>>q>>w;
if(n<=5000 && q<=5000)
{
vector<pair<long long,long long>> edges;
for(long long n1=n-1;n1>0;n1--)
{
long long a,b,c;
cin>>a>>b>>c;
edges.push_back({a,b});
adj[a].push_back({b,c});
adj[b].push_back({a,c});
}
long long last=0;
for(;q>0;q--)
{
long long d,e;
cin>>d>>e;
d=(d+last)%(n-1);
e=(e+last)%w;
pair<long long,long long> par=edges[d];
for(long long i=0;i<adj[par.first].size();i++)
{
if(adj[par.first][i].first==par.second)
{
adj[par.first][i].second=e;
}
}
for(long long i=0;i<adj[par.second].size();i++)
{
if(adj[par.second][i].first==par.first)
{
adj[par.second][i].second=e;
}
}
memset(dist,-1,sizeof(dist));
dfs(1,0);
pair<long long,long long> maxx={0,0};
for(long long i=1;i<=n;i++)
{
maxx=max(maxx,{dist[i],i});
}
long long br=maxx.second;
memset(dist,-1,sizeof(dist));
dfs(br,0);
pair<long long,long long> maxx2={0,0};
for(long long i=1;i<=n;i++)
{
maxx2=max(maxx2,{dist[i],i});
}
last=maxx2.first;
cout<<last<<endl;
}
}
else
{
long long arr[n]={};
vector<pair<long long,long long>> edges;
set<pair<long long,long long>> st;
for(long long i=0;i<n-1;i++)
{
long long a,b,c;
cin>>a>>b>>c;
edges.push_back({a,b});
adj[a].push_back({b,c});
adj[b].push_back({a,c});
arr[i]=c;
st.insert({-c,i});
}
long long last=0;
for(;q>0;q--)
{
long long d,e;
cin>>d>>e;
d=(d+last)%(n-1);
e=(e+last)%w;
st.erase({-arr[d],d});
arr[d]=e;
st.insert({-e,d});
long long br=2;
long long res=0;
for(auto it : st)
{
if(br==0)
break;
res-=it.first;
br--;
}
last=res;
cout<<res<<endl;
}
}
return 0;
}
