#include<bits/stdc++.h>
using namespace std;
#define mp make_pair
#define INF 10000000
#define MOD 1000000007
#define MID ((l+r)/2)
#define HASHMOD 2305843009213693951
#define ll long long
#define ull unsigned long long
#define F first
#define S second
typedef pair<ll, ll> ii;
typedef pair<ii, ll> iii;
typedef vector<ll> vi;
typedef vector<ii> vii;
typedef map<ll, ll> mii;
#define EPS 1e-6
#define FOR(i,n) for(int i=0;i<((int)(n));i++)
#define FORi(i,a,b) for(int i=((int)(a));i<((int)(b));i++)
#define FOA(v, a) for(auto v : a)
ll t, n;
vi a, b;
vector<vii> adj;
ii f;
ll cnt=0;
vector<int> dfso;
void dfs(int s, int p=-1, ll d=0){
dfso[s] = cnt++;
if(d>f.F) f = max(f, {d, s});
FOA(v, adj[s]){
if(v.F!=p) dfs(v.F, s, d+v.S);
}
}
vector<int> pr;
struct node{
ii l1={0,0}, l2={0,0};
int w=0;
int id=1;
ll ans=0;
vector<node*> c;
vector<node*> all_c;
void build(int p=-1){
pr.push_back(id);
FOA(v,adj[id]){
if(v.F!=p){
c.push_back(new node());
c[c.size()-1]->w = v.S;
c[c.size()-1]->id = v.F;
c[c.size()-1]->build(id);
}
}
FOA(v, c){
if(v->w + v->l1.F > l1.F) l2 = l1, l1 = {v->l1.F + v->w, v->id};
else if(v->w + v->l1.F > l2.F && v->id != l1.S) l2 = {v->l1.F + v->w, v->id};
ans = max(ans, v->ans);
//else if(v->w + v->l2 > l2) l2 = v->l2 + v->w;
}
ans = max(ans, l1.F + l2.F);
//cout<<id<<" ("<<l1.F<<" "<<l1.S<<") ("<<l2.F<<" "<<l2.S<<")"<<" "<<ans<<endl;
}
void update(int s, ll t){
int pos = c.size()-1;
FOR(i,c.size()-1){
if(dfso[c[i]->id] <= dfso[s] && dfso[s] < dfso[c[i+1]->id]) pos = i;
}
if(s==id){
//cout<<"CHAINGE "<<s<<endl;
w = t;
}
else{
c[pos]->update(s, t);
//node*v = c[pos];
l1 = {0,0}, l2 = {0,0};
ans = 0;
FOA(v, c){
if(v->w + v->l1.F > l1.F) l2 = l1, l1 = {v->l1.F + v->w, v->id};
else if(v->w + v->l1.F > l2.F && v->id != l1.S) l2 = {v->l1.F + v->w, v->id};
ans = max(ans, v->ans);
}
ans = max(ans, l1.F + l2.F);
//cout<<id<<" ("<<l1.F<<" "<<l1.S<<") ("<<l2.F<<" "<<l2.S<<")"<<" "<<ans<<endl;
}
}
};
int main(){
int q;
ll w;
cin>>n>>q>>w;
adj.assign(n+1, vii());
dfso.assign(n+1, 0);
vector<pair<ii,ii> > edg(n-1);
set<ii> ws;
vi wu(n);
FOR(i,n-1){
ll a, b, c;
cin>>a>>b>>c;
ws.insert({-c, i});
wu[i] = c;
edg[i] = {{a, adj[a].size()}, {b, adj[b].size()}};
adj[a].push_back({b,c});
adj[b].push_back({a,c});
}
node root;
root.build();
ll last=0;
dfs(1);
//FOR(i,n) cout<<dfso[i+1]<<" "; cout<<endl;
while(q--){
ll a, b;
cin>>a>>b;
//cout<<"UPDATE\n";
a= (a + last) % (n-1);
b = (b+last) % w;
adj[edg[a].F.F][edg[a].F.S].S = b;
adj[edg[a].S.F][edg[a].S.S].S = b;
f = {0,1};
//dfs(1);
//dfs(f.S);
//cout<<a<<" "<<b<<endl;
//cout<<"edg "<<edg[a].F.F<<" "<<edg[a].S.F<<endl;
int upn = max(ii(dfso[edg[a].F.F], edg[a].F.F),ii(dfso[edg[a].S.F], edg[a].S.F)).S;
//cout<<"pos "<<upn<<endl;
root.update(upn, b);
//last = f.F;
last = root.ans;
cout<<last<<endl;
}
}
