#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
void solve(){
int n, q, wlim;
cin>>n>>q>>wlim;
vector<array<int, 3>> edges(n - 1);
vector<vector<pair<int, int>>> adj(n + 1);
for(int i = 0; i < n - 1; ++i){
int u, v, w;
cin>>u>>v>>w;
edges[i] = {u, v, w};
adj[u].push_back(make_pair(v, i));
adj[v].push_back(make_pair(u, i));
}
vector<int> weight(n - 1);
for(int i = 0; i < n - 1; ++i)
weight[i] = edges[i][2];
vector<int> depth(n + 1), parent(n + 1), from_edge(n + 1);
function<void(int, int)> dfs = [&](int u, int p){
for(int i = 0; i < adj[u].size(); ++i){
int v = adj[u][i].first;
int idx = adj[u][i].second;
if(v == p) continue;
depth[v] = depth[u] + weight[idx];
parent[v] = u;
from_edge[v] = idx;
dfs(v, u);
}
};
dfs(1, -1);
vector<int> max1(n + 1), max2(n + 1);
function<int(int)> dfs_depths = [&](int u){
int d1 = 0, d2 = 0;
for(int i = 0; i < adj[u].size(); ++i){
int v = adj[u][i].first;
int idx = adj[u][i].second;
if(v == parent[u]) continue;
int d = dfs_depths(v) + weight[idx];
if(d > d1){
d2 = d1;
d1 = d;
}else if(d > d2){
d2 = d;
}
}
max1[u] = d1;
max2[u] = d2;
return d1;
};
dfs_depths(1);
int result = max1[1] + max2[1];
while(q--){
int x, y;
cin>>x>>y;
x = (x + result) % (n - 1);
y = (y + result) % wlim;
int u = edges[x][0], v = edges[x][1];
if(parent[v] == u) swap(u, v);
int diff = y - weight[x];
weight[x] = y;
int curr = v;
while(true){
int d1 = 0, d2 = 0;
for(int i = 0; i < adj[curr].size(); ++i){
int child = adj[curr][i].first;
int idx = adj[curr][i].second;
if(child == parent[curr]) continue;
int d = max1[child] + weight[idx];
if(d > d1){
d2 = d1;
d1 = d;
}else if(d > d2){
d2 = d;
}
}
if(max1[curr] == d1 && max2[curr] == d2) break;
max1[curr] = d1;
max2[curr] = d2;
if(curr == 1) break;
curr = parent[curr];
}
result = max1[1] + max2[1];
cout<<result<<'\n';
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int t = 1;
//cin>>t;
while(t--){
solve();
}
}
