#ifdef LOCAL
#include "stdafx.h"
#else
#include <bits/stdc++.h>
#define IL inline
#define LL long long
#define eb emplace_back
#define sz(v) ((int) (v).size())
#define me(f, x) memset(f, x, sizeof(f))
#define mc(f, g) memcpy(f, g, sizeof(g))
#define L(i, j, k) for (int i = (j); i <= (k); ++i)
#define R(i, j, k) for (int i = (j); i >= (k); --i)
#define FIO(FILE) freopen(FILE".in", "r", stdin), freopen(FILE".out", "w", stdout)
using namespace std;

using vi = vector<int>;
#endif

constexpr int N = 2e5 + 9;
constexpr LL INF = 0x3f3f3f3f3f3f3f3f;
int n, a[N], b[N];
LL V;
vi g[N];

int lab[N];

int pdfs (int u, int f) {
  int msk = 0, ban = 0;
  for (int v : g[u]) {
    if (v ^ f) {
      int x = pdfs(v, u);
      msk |= ban & x;
      ban |= x;
    }
  }
  int l = msk ? 32 - __builtin_clz(msk) : 0;
  lab[u] = __builtin_ctz((ban >> l) + 1) + l;
  return (ban >> lab[u] | 1) << lab[u];
}

int nx[N];
struct item {
  LL x, y;
  int z;
} A[N], B[N];

LL ans = INF;

void conq (int l, int r) {
  if (l == r) {
    if (A[l].x == 0) {
      ans = min(ans, A[l].y);
    }
    return;
  }
  int m = (l + r) >> 1;
  conq(l, m);
  conq(m + 1, r);
  nx[r] = -1;
  R (i, r - 1, m + 1) {
    nx[i] = B[i].z != B[i + 1].z ? i + 1 : nx[i + 1];
  }
  int j = m + 1;
  L (i, l, m) {
    while (j <= r && B[j].y < A[i].x) {
      ++j;
    }
    if (j > r) {
      break;
    }
    int p = A[i].z == B[j].z ? nx[j] : j;
    if (~p) {
      ans = min(ans, A[i].y + B[p].y);
    }
  }
  inplace_merge(A + l, A + m + 1, A + r + 1, [] (item a, item b) {
    return a.x < b.x;
  });
  inplace_merge(B + l, B + m + 1, B + r + 1, [] (item a, item b) {
    return a.y < b.y;
  });
}

bool vis[N];

int sq[N], dfc, col[N], ed[N];
LL mn[N], sb[N];

void dfs (int u, int f, int o) {
  col[u] = o;
  sq[++dfc] = u;
  sb[u] = sb[f] + b[u];
  mn[u] = min(mn[f], (LL)a[u]);
  if (o != -1) {
    ed[o] = dfc;
  }
  for (int v : g[u]) {
    if (v == f || vis[v]) {
      continue;
    }
    dfs(v, u, o == -1 ? v : o);
  }
}

int ord[N];

void dfz (int u) {
  vis[u] = true;
  dfc = 0;
  dfs(u, 0, -1);
  L (i, 1, dfc) {
    ord[i] = sq[i];
  }
  sort(ord + 1, ord + dfc + 1, [] (int x, int y) {
    return mn[x] < mn[y];
  });
  L (i, 1, dfc) {
    int v = ord[i];
    LL l = max(0LL, (V + mn[v] - 1) / mn[v] - sb[v]);
    A[i] = {l, sb[v], col[v]};
    B[i] = {-1, sb[v] - b[u], col[v]};
  }
  conq(1, dfc);
  int st = 1;
  for (int v : g[u]) {
    if (!vis[v]) {
      int rt = v;
      L (i, st + 2, ed[v]) {
        if (lab[sq[i]] > lab[rt]) {
          rt = sq[i];
        }
      }
      st = ed[v];
      dfz(rt);
    }
  }
}

int main () {
  ios::sync_with_stdio(0), cin.tie(0);
  cin >> n >> V;
  L (i, 1, n) {
    cin >> a[i] >> b[i];
  }
  L (i, 1, n - 1) {
    int u, v;
    cin >> u >> v;
    g[u].eb(v);
    g[v].eb(u);
  }
  pdfs(1, 0);
  mn[0] = INF;
  int Rt = 1;
  L (i, 2, n) {
    if (lab[i] > lab[Rt]) {
      Rt = i;
    }
  }
  dfz(Rt);
  cout << ans << '\n';
}
// I love WHQ!