#include <bits/stdc++.h>

#define rep(i, j, k) for (int i = (j); i <= (k); ++i)
#define per(i, j, k) for (int i = (j); i >= (k); --i)
#define SZ(v) int((v).size())
#define ALL(v) (v).begin(),(v).end()
#define fi first
#define se second
using ll = long long;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;

template<class T>inline void chkmn(T &x, T y) { if (y < x) x = y; }
template<class T>inline void chkmx(T &x, T y) { if (y > x) x = y; }

using namespace std;

const int maxn = 200010;

int n, sz[maxn], mxsz[maxn], vis[maxn], bel[maxn], id[maxn], pid[maxn], L[maxn], R[maxn], len, tot, asz, rt;
ll a[maxn], b[maxn], lim, mna[maxn], sumb[maxn], ans, cmn;
vector<int> e[maxn];

void findrt(int u, int fa) {
  sz[u] = 1, mxsz[u] = 0;
  for (int v : e[u]) {
    if (v == fa || vis[v]) continue;
    findrt(v, u), sz[u] += sz[v];
    chkmx(mxsz[u], sz[v]);
  }
  chkmx(mxsz[u], asz - sz[u]);
  if (mxsz[u] <= asz / 2) rt = u;
}

void dfs(int u, int fa, int be) {
  bel[u] = be, id[++len] = u, sz[u] = 1;
  for (int v : e[u]) {
    if (v == fa || vis[v]) continue;
    mna[v] = min(mna[u], a[v]), sumb[v] = sumb[u] + b[v];
    dfs(v, u, be), sz[u] += sz[v];
  }
}

void fz(int l, int r, int u) {
  if (l == r) {
    sort(id + L[l], id + R[l] + 1, [&](int x, int y) { return mna[x] > mna[y]; });
    return;
  }
  int mid = (l + r) >> 1;
  fz(l, mid, u), fz(mid + 1, r, u);
  int cl = L[l], cr = R[mid], dl = L[mid + 1], dr = R[r], tot = cl - 1;
  set<ll> S;
  int pos = dl;
  rep (i, cl, cr) {
    while (pos <= dr && mna[id[pos]] >= mna[id[i]]) {
      S.insert(sumb[id[pos]]), pos++;
    }
    auto it = S.lower_bound((lim + mna[id[i]] - 1) / mna[id[i]] - sumb[id[i]] - b[u]);
    if (it != S.end()) chkmn(cmn, *it + sumb[id[i]] + b[u]);
  }
  S.clear(), pos = cl;
  rep (i, dl, dr) {
    while (pos <= cr && mna[id[pos]] >= mna[id[i]]) {
      S.insert(sumb[id[pos]]), pid[++tot] = id[pos++];
    }
    auto it = S.lower_bound((lim + mna[id[i]] - 1) / mna[id[i]] - sumb[id[i]] - b[u]);
    if (it != S.end()) chkmn(cmn, *it + sumb[id[i]] + b[u]);
    pid[++tot] = id[i];
  }
  while (pos <= cr) pid[++tot] = id[pos++];
  rep (i, cl, dr) id[i] = pid[i];
}

void solve(int u) {
  vis[u] = 1, id[len = 1] = u, L[1] = R[1] = 1;
  if (a[u] * b[u] >= lim) chkmn(ans, b[u]);
  mna[u] = a[u], sumb[u] = 0, bel[u] = (tot = 1);
  for (int v : e[u]) {
    if (vis[v]) continue;
    mna[v] = min(a[u], a[v]), sumb[v] = b[v];
    L[++tot] = len + 1, dfs(v, u, tot), R[tot] = len;
  }
  cmn = 1e18, fz(1, tot, u), chkmn(ans, cmn);
  for (int v : e[u]) {
    if (vis[v]) continue;
    asz = sz[v], findrt(v, u), solve(rt);
  }
}

int main() {
  cin.tie(nullptr) -> ios::sync_with_stdio(false);
  cin >> n >> lim;
  rep (i, 1, n) cin >> a[i] >> b[i];
  rep (i, 1, n - 1) {
    int u, v;
    cin >> u >> v;
    e[u].emplace_back(v);
    e[v].emplace_back(u);
  }
  ans = 1e18, asz = n, findrt(1, 0), solve(rt);
  cout << ans << '\n';
}