#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ii = pair<ll, ll>;
#define foru(i, l, r) for(int i=(l); i<=(r); ++i)
#define ford(i, l, r) for(int i=(l); i>=(r); --i)
#define fore(x, v) for(auto &x : v)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define fi first
#define se second
#define file "input"
template<class T> bool minimize(T &a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> bool maximize(T &a, T b) { if (a < b) { a = b; return 1; } return 0; }
void setIO() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
if (fopen(file".inp", "r")) {
freopen(file".inp", "r", stdin);
freopen(file".out", "w", stdout);
}
}
const int MOD = 998244353;
const int N = 1e5+5;
struct edge {
int u, v;
ll w;
int oth(int x) { return u^v^x; }
};
vector<edge> e;
bool allstar = 1, bintree = 1;
int n, q, up[N], par[N];
ll W;
vector<int> adj[N];
ll f[N];
ii nax[N];
set<ii> al;
void dfs_first(int u, int p, int h) {
if (h > 20) bintree = 0;
nax[u] = {0, 0};
fore(i, adj[u]) {
int v = e[i].oth(u);
if (v == p) continue;
up[i] = u;
par[v] = u;
dfs_first(v, u, h+1);
maximize(f[u], f[v] + e[i].w);
ll tmp = f[v] + e[i].w;
if (tmp > nax[u].fi) swap(nax[u].fi, nax[u].se), nax[u].fi = tmp;
else if (tmp > nax[u].se) nax[u].se = tmp;
}
al.insert({-nax[u].fi-nax[u].se, u});
}
void recalc(int u) {
al.erase({-nax[u].fi-nax[u].se, u});
nax[u] = {0, 0};
f[u] = 0;
fore(i, adj[u]) {
int v = e[i].oth(u);
if (v == par[u]) continue;
maximize(f[u], f[v] + e[i].w);
ll tmp = f[v] + e[i].w;
if (tmp > nax[u].fi) swap(nax[u].fi, nax[u].se), nax[u].fi = tmp;
else if (tmp > nax[u].se) nax[u].se = tmp;
}
al.insert({-nax[u].fi-nax[u].se, u});
}
int main() {
setIO();
cin >> n >> q >> W;
e = vector<edge>(n-1);
foru(i, 0, n-2) {
int u, v;
ll w;
cin >> u >> v >> w;
e[i] = {u, v, w};
adj[u].push_back(i);
adj[v].push_back(i);
}
allstar = (sz(adj[1]) == n-1);
foru(i, 1, n) bintree &= (sz(adj[i]) > 2);
if (allstar) foru(i, 0, n-2) al.insert({-e[i].w, i});
else dfs_first(1, 0, 0);
ll lst = 0;
foru(i, 1, q) {
ll ds, es;
cin >> ds >> es;
ds = (ds + lst) % (n - 1);
es = (es + lst) % W;
if (allstar) {
al.erase({-e[ds].w, ds});
e[ds].w = es;
al.insert({-e[ds].w, ds});
if (sz(al) == 1) lst = -(al.begin()->first);
else lst = -(al.begin()->first + next(al.begin())->first);
}
else {
int u = up[ds];
e[ds].w = es;
while (true) {
recalc(u);
if (u == 1) break;
u = par[u];
}
lst = -(al.begin()->first);
}
cout << lst << "\n";
}
}
