#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
typedef long long ll;
vector<bool> w;
vector<int> pa, sz, zs;
vector<ll> ec;
vector<vector<int> > v, wl, wr, in, de, ut, ox;
vector<vector<ll> > ed, sg, lz;
multiset<ll> se;
vector<multiset<ll> > sm;
int t, J, L, R;
void bl(int j, int i, int l, int r)
{
if (sg[j].size() <= i)
{
sg[j].resize(i + 1);
lz[j].resize(i + 1);
wl[j].resize(i + 1);
wr[j].resize(i + 1);
}
sg[j][i] = lz[j][i] = 0;
wl[j][i] = l;
wr[j][i] = r;
if (r - l > 1)
{
bl(j, (i << 1), l, ((l + r) >> 1));
bl(j, ((i << 1) ^ 1), ((l + r) >> 1), r);
}
}
void ps(int j, int i)
{
if ((i << 1) < sg[j].size())
{
sg[j][i << 1] += lz[j][i];
lz[j][i << 1] += lz[j][i];
}
if (((i << 1) ^ 1) < sg[j].size())
{
sg[j][(i << 1) ^ 1] += lz[j][i];
lz[j][(i << 1) ^ 1] += lz[j][i];
}
lz[j][i] = 0;
}
void upd(int i, ll x)
{
ps(J, i);
if (wl[J][i] >= R || wr[J][i] <= L)
return;
if (wl[J][i] >= L && wr[J][i] <= R)
{
sg[J][i] += x;
lz[J][i] += x;
ps(J, i);
return;
}
upd(i << 1, x);
upd((i << 1) ^ 1, x);
sg[J][i] = max(sg[J][i << 1], sg[J][(i << 1) ^ 1]);
}
ll qu(int j, int i, int l, int r)
{
ps(j, i);
if (wl[j][i] >= r || wr[j][i] <= l)
return 0;
if (wl[j][i] >= l && wr[j][i] <= r)
return sg[j][i];
return max(qu(j, (i << 1), l, r), qu(j, ((i << 1) ^ 1), l, r));
}
void dfs(int i, int p, int u, int k, int d)
{
in[i].push_back(t);
de[i].push_back(d);
if (k != -1)
ox[i].push_back(k);
else
ox[i].push_back(u);
t++;
for (auto h : v[i])
{
if (h == p || w[h])
continue;
if (i == u)
dfs(h, i, u, h, d + 1);
else
dfs(h, i, u, k, d + 1);
}
ut[i].push_back(t);
}
void fsz(int i, int p)
{
sz[i] = 1;
for (auto h : v[i])
{
if (h == p || w[h])
continue;
fsz(h, i);
sz[i] += sz[h];
}
}
int fcd(int i, int p, int n)
{
for (auto h : v[i])
{
if (h == p || w[h])
continue;
if (sz[h] * 2 > n)
return fcd(h, i, n);
}
return i;
}
void cd(int i, int p)
{
fsz(i, -1);
int n = sz[i];
int u = fcd(i, -1, n);
pa[u] = p;
zs[u] = n;
w[u] = 1;
t = 0;
dfs(u, -1, u, -1, 0);
for (auto h : v[u])
{
if (w[h])
continue;
sm[u].insert(0);
cd(h, u);
}
}
void ud(int a, int b, ll x)
{
int i, j, k, tc, ts, l;
ll mx;
i = de[a].size() - 1;
for (j = a; j != -1; j = pa[j])
{
if (j == b)
break;
i--;
}
if (j == -1)
{
swap(a, b);
i = de[a].size() - 1;
for (j = a; j != -1; j = pa[j])
{
if (j == b)
break;
i--;
}
}
k = de[b].size() - 1;
for (j = b; j != -1; j = pa[j])
{
if (de[a][i] > de[b][k])
ts = ox[a][i];
else
ts = ox[b][k];
l = de[ts].size() - 1;
for (tc = ts; tc != -1; tc = pa[tc])
{
if (tc == j)
break;
l--;
}
mx = qu(j, 1, in[ts][l], ut[ts][l]);
sm[j].erase(sm[j].find(mx));
if (de[a][i] > de[b][k])
{
J = j;
L = in[a][i];
R = ut[a][i];
upd(1, x);
}
else
{
J = j;
L = in[b][k];
R = ut[b][k];
upd(1, x);
}
mx = qu(j, 1, in[ts][l], ut[ts][l]);
sm[j].insert(mx);
i--;
k--;
se.erase(se.find(ec[j]));
auto it = sm[j].end();
if (it == sm[j].begin())
ec[j] = 0;
else
{
it--;
ec[j] = (*it);
if (it != sm[j].begin())
{
it--;
ec[j] += (*it);
}
}
se.insert(ec[j]);
}
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int n, q, i;
ll a, b, c, W, la = 0;
cin >> n >> q >> W;
v.resize(n);
ed.resize(n - 1);
pa.resize(n);
sz.resize(n);
zs.resize(n);
sg.resize(n);
lz.resize(n);
wl.resize(n);
wr.resize(n);
in.resize(n);
de.resize(n);
ut.resize(n);
w.resize(n);
ec.resize(n);
sm.resize(n);
ox.resize(n);
for (i = 0; i < n; i++)
{
pa[i] = -1;
w[i] = 0;
ec[i] = 0;
se.insert(0);
}
for (i = 0; i < n - 1; i++)
{
cin >> a >> b >> c;
a--;
b--;
v[a].push_back(b);
v[b].push_back(a);
ed[i] = {a, b, c};
}
cd(0, -1);
for (i = 0; i < n; i++)
bl(i, 1, 0, zs[i]);
for (auto g : ed)
ud(g[0], g[1], g[2]);
while (q--)
{
cin >> a >> b;
a += la;
a %= n - 1;
b += la;
b %= W;
ud(ed[a][0], ed[a][1], b - ed[a][2]);
ed[a][2] = b;
auto it = se.end();
it--;
la = (*it);
cout << la << '\n';
}
}
