#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <iostream>
#include <vector>
#include <queue>
#include <cassert>
#include <set>
#include <ctime>

using namespace std;

#define int long long
#define pb push_back
#define PII pair<int,int>
#define x first
#define y second
#define For(i, l, r) for(int i = l; i <= r; i ++)
#define Rep(i, l, r) for(int i = l; i >= r; i --)

bool START;

void in(int &x)
{
	char c = getchar(); int op = 1;
	while(c > '9' || c < '0') op *= (c == '-' ? -1 : 1), c = getchar();
	for(x = 0; c >= '0' && c <= '9'; c = getchar()) x = x * 10 + c - '0'; x *= op;
}

const int N = 2e5+ 50, oo = 1e18+ 10;

int n, m, V;
int a[N], b[N];
vector<int> G[N];
bool vis[N];
int wc, all, sz[N], ans;

void gsz(int u, int pa)
{
	sz[u] = 1;
	for(int v:G[u])if(v!=pa&&!vis[v]) 
	{
		gsz(v, u); sz[u] += sz[v];
	}
}

struct node
{
	int u, c, w;
	bool operator < (const node &t) {return w > t.w;}
};

node son[N];
int cnt;

void grt(int u, int pa)
{
	int tmp = all - sz[u];
	for(int v:G[u])if(v!=pa&&!vis[v]) 
	{
		grt(v, u); tmp = max(tmp, sz[v]);
	}
	if(tmp * 2 <= all) wc = u;
}

int num[N], sum[N], mn[N];

void dfs1(int u, int pa, int ss, int mm, int z)
{
	ss += b[u]; mm = min(mm, a[u]);
	mn[u] = mm; sum[u] = ss;
	son[++ cnt] = (node){u, z, mn[u]};
	for(int v:G[u])if(v!=pa&&!vis[v]) 
		dfs1(v, u, ss, mm, z);
}

struct dat
{
	PII mx, sec; 
	void ins(PII E)
	{
		if(E.x < mx.x)
		{
			if(mx.y == E.y) mx = E;
			else sec = mx, mx = E;
		}
		else
		{
			if(E.y != mx.y && E.x < sec.x) sec = E;
		}
	}
};

namespace BIT
{
	int n;
	dat c[N];
	void clear(int nn) {n = nn; For(i ,1, nn) c[i] = (dat){{oo, 0}, {oo, 0}};}
	void upd(int x, int y, int z)
	{
		PII E = {y, z};
		while(x)
		{
			c[x].ins(E);
			x -= x & (-x);
		}
	}
	int qmin(int x, int z)
	{
		int res = oo;
		while(x <= n)
		{
			if(c[x].mx.y != z) res = min(res, c[x].mx.x);
			if(c[x].sec.y != z) res = min(res, c[x].sec.x);
			x += x & (-x);
		}
		return res;
	}
}

void Work(int u)
{
	gsz(u, 0); wc = u; all = sz[u]; grt(u, 0);
	u = wc;
	vis[u] = 1;
	cnt = 0; num[0] = 0;
	for(int v : G[u]) if(!vis[v])
	{
		dfs1(v, u, 0, a[u], v);
	}
	For(i, 1, cnt)
	{
		if((sum[son[i].u] + b[u]) * mn[son[i].u] >= V) ans = min(ans, sum[son[i].u] + b[u]);
		num[++ num[0]] = sum[son[i].u];
	}
	sort(num + 1, num + num[0] + 1);
	num[0] = unique(num + 1, num + num[0] + 1) - num - 1;
	sort(son + 1, son + cnt + 1);
	BIT::clear(num[0]);
	For(i, 1, cnt)
	{
		int x = son[i].u, m2 = mn[x], s2 = sum[x], lim = (V + m2 - 1) / m2 - s2 - b[u];
		int k = lower_bound(num + 1, num + num[0] + 1, lim) - num;
		if(k <= num[0])
		{
			ans = min(ans, b[u] + s2 + BIT::qmin(k, son[i].c));
		// For(j, 1, i - 1) if(sum[son[j].u] >= lim && son[j].c != son[i].c) ans = min(ans, sum[son[j].u] + b[u] + s2);
		}
		k = lower_bound(num + 1, num + num[0] + 1, s2) - num;
		BIT::upd(k, s2, son[i].c);
	}
	for(int v : G[u]) if(!vis[v]) Work(v);
}

bool ENDPOS = 0;
signed main()
{
	double chu = clock();
	in(n); in(V);
	For(i, 1, n) in(a[i]), in(b[i]);
	For(i, 2, n)
	{
		int u, v; in(u); in(v);
		G[u].pb(v); G[v].pb(u);
	}
	ans = oo;
	For(i, 1, n) if(a[i] * b[i] >= V) ans = min(ans, b[i]);
	Work(1);
	printf("%lld\n", ans);
	cerr << "Time = " << (clock() - chu) * 1.0 / CLOCKS_PER_SEC << " s" <<  endl;
	return 0;
}