#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 3e5+5;
vector<array<int, 2>> g[N];
int in[N], sub[N];
int C = 1;
int dis[N];
void dfs(int u, int p){
in[u] = C++;
sub[u] = 1;
for(auto [to, w]: g[u]){
if(to == p) continue;
dis[to] = dis[u] + w;
dfs(to, u);
sub[u] += sub[to];
}
}
struct Segtree {
vector<int> sg, lz;
void fill(int n) { sg.assign(n*4, 0); lz.assign(n*4, 0); }
void push(int u, int l, int r){
sg[u] += (r-l+1) * lz[u];
if(l != r){
lz[u*2] += lz[u];
lz[u*2+1] += lz[u];
}
lz[u] = 0;
}
void update(int u, int l, int r, int x, int y, int v){
push(u, l, r);
if(y < l or x > r) return;
if(x <= l and y >= r) {
lz[u] += v;
push(u, l, r);
return;
}
int m = (l+r)/2;
update(u*2, l, m, x, y, v);
update(u*2+1, m+1, r, x, y, v);
sg[u] = max(sg[u*2], sg[u*2+1]);
}
int get(int u, int l, int r, int x, int y){
push(u, l, r);
if(y < l or x > r) return 0;
if(x <= l and y >= r) return sg[u];
int m = (l+r)/2;
auto a1 = get(u*2, l, m, x, y);
auto a2 = get(u*2+1, m+1, r, x, y);
return max(a1, a2);
}
};
// for(int i=1; i<=n; i++)
void solve(){
int n, q, W; cin >> n >> q >> W;
vector<array<int, 3>> input;
for(int i=1; i<n; i++) {
int x, y, w; cin >> x >> y >> w;
input.push_back({x, y, w});
g[x].push_back({y, w});
g[y].push_back({x, w});
}
dfs(1, 0);
Segtree sg;
sg.fill(n);
for(int i=1; i<=n; i++) {
sg.update(1, 1, n, in[i], in[i], dis[i]);
}
int last = 0;
while(q--){
int d, aft; cin >> d >> aft;
d = (d+last)%(n-1);
aft = (aft+last)%W;
auto [u, v, bef] = input[d];
sg.update(1, 1, n, in[v], in[v]+sub[v]-1, aft-bef);
input[d][2] = aft;
vector<int> V = {0, 0};
for(auto [to, w]: g[1]){
// cout << sg.get(1, 1, n, in[to], in[to]+sub[to]-1) << endl;
V.push_back(sg.get(1, 1, n, in[to], in[to]+sub[to]-1));
}
sort(V.rbegin(), V.rend());
// cout << aft-bef << endl;
cout << V[0]+V[1] << '\n';
// cout << ans[0] << '\n';
}
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
solve();
}
