#include <bits/stdc++.h>

#define ls (o << 1)

#define rs (o << 1 | 1)

#define LL long long

#define INF 1e18

using namespace std;

const int maxn = 100010;

int lp[maxn], rp[maxn], mp[maxn * 2], tot;

vector<pair<int, long long> > G[maxn];

LL d[maxn];

void add(LL x, LL y, LL z) {

	G[x].push_back(make_pair(y, z));

	G[y].push_back(make_pair(x, z));

}

struct edge {

	int u, v;

	LL w;

};

edge a[maxn];

struct Seg {

	LL v[6], lz;

	//0: a

	//1: b

	//2: c

	//3: a + 2 * b

	//4: 2 * c + b

	//5: a + b + 2 * c

};

Seg tr[maxn * 8];

void pushup(int o) {

	//0:

	tr[o].v[0] = max(tr[ls].v[0], tr[rs].v[0]);

	//1:

	tr[o].v[1] = max(tr[ls].v[1], tr[rs].v[1]);

	//2:

	tr[o].v[2] = max(tr[ls].v[2], tr[rs].v[2]);

	//3:

	tr[o].v[3] = max(tr[ls].v[3], tr[rs].v[3]);

	tr[o].v[3] = max(tr[o].v[3], tr[ls].v[0] + 2ll * tr[rs].v[1]);

	//4:

	tr[o].v[4] = max(tr[ls].v[4], tr[rs].v[4]);

	tr[o].v[4] = max(tr[o].v[4], 2ll * tr[ls].v[1] + tr[rs].v[2]);

	//: 5

	tr[o].v[5] = max(tr[ls].v[5], tr[rs].v[5]);

	tr[o].v[5] = max(tr[o].v[5], tr[ls].v[3] + tr[rs].v[2]);

	tr[o].v[5] = max(tr[o].v[5], tr[ls].v[0] + tr[rs].v[4]);

}

void maintain(int o, LL x) {

	tr[o].lz += x;

	tr[o].v[0] += x;

	tr[o].v[1] -= x;

	tr[o].v[2] += x;

	tr[o].v[3] -= x;

	tr[o].v[4] -= x;

}

void pushdown(int o) {

	if(tr[o].lz) {

		maintain(ls, tr[o].lz);

		maintain(rs, tr[o].lz);

		tr[o].lz = 0;

	}

}

void build(int o, int l, int r) {

	tr[o].lz = 0;

	if(l == r) {

		tr[o].v[0] = tr[o].v[2] = d[mp[l]];

		tr[o].v[4] = tr[o].v[3] = tr[o].v[1] = -d[mp[l]];

		tr[o].v[5] = 0;

		return;

	}

	int mid = (l + r) >> 1;

	build(ls, l, mid);

	build(rs, mid + 1, r);

	pushup(o);

}

void update(int o, int l, int r, int ql, int qr, LL val) {

	if(l >= ql && r <= qr) {

		maintain(o, val);

		return;

	}

	int mid = (l + r) >> 1;

	pushdown(o);

	if(ql <= mid) update(ls, l, mid, ql, qr, val);

	if(qr > mid) update(rs, mid + 1, r, ql, qr, val);

	pushup(o);

}

void dfs(int x, int fa, LL dis) {

	mp[++tot] = x;

	lp[x] = tot;

	rp[x] = tot;

	d[x] = dis;

	for (auto y : G[x]) {

		if(y.first == fa) continue;

		dfs(y.first, x, dis + y.second);

		mp[++tot] = x;

		rp[x] = tot;

	}

}

int main() {

	int n, m;

	LL w, x, y, z;

	scanf("%d%d%lld", &n, &m, &w);

	for (int i = 1; i < n; i++) {

		scanf("%lld%lld%lld", &x, &y, &z);

		add(x, y, z);

		a[i].u = x, a[i].v = y, a[i].w = z;

	}

	dfs(1, 0, 0);

	build(1, 1, tot);

	LL ans = 0;

	while(m--) {

		scanf("%lld%lld", &x, &y);

		x = (x + ans) % (n - 1) + 1;

		y = (y + ans) % w;

		int p;

		if(lp[a[x].u] < lp[a[x].v]) p = a[x].v;

		else p = a[x].u;

		update(1, 1, tot, lp[p], rp[p], y - a[x].w);

		a[x].w = y;

		ans = tr[1].v[5];

		printf("%lld\n", ans);

	}

}