#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
#define ll long long
ll mod = 998244353;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll binpow(ll a, ll b)
{
ll res = 1;
while (b>0)
{
if (b&1)
res = (res*a)%mod;
a = (a*a)%mod;
b>>=1;
}
return res;
}
ll gcd(ll x, ll y)
{
if (y==0)
return x;
return gcd(y, x%y);
}
const ll maxi = 303030;
vector<vector<ll>>g(maxi);
vector<ll>vis(maxi, 0);
vector<ll>v(maxi);
priority_queue<pair<ll,ll>, vector<pair<ll,ll>>, greater<pair<ll,ll>>>pq[maxi];
vector<ll>adr(maxi);
ll merge(ll a, ll b)
{
if (pq[a].size()<pq[b].size()) swap(a, b);
while (!pq[b].empty())
{
pq[a].push(pq[b].top());
pq[b].pop();
}
return a;
}
void add(ll x, pair<ll,ll>p)
{
while (!pq[x].empty())
{
auto t = pq[x].top();
if (p.second<=0)
{
pq[x].pop();
p.first = max(p.first, t.first-p.second);
p.second += t.second;
}
else
{
if (t.first<p.first)
{
pq[x].pop();
p.second += t.second;
}
else
{
pq[x].push(p);
break;
}
}
}
if (pq[x].empty())
{
if (p.second>=0)
pq[x].push(p);
}
}
void dfs(ll x)
{
vis[x] = 1;
ll f = 0;
adr[x] = x;
for (auto i:g[x])
{
if (vis[i]==0)
{
dfs(i);
// if (x==0) cout<<"H"<<endl;
if (!f)
{
f = 1;
adr[x] = adr[i];
}
else
{
adr[x] = merge(adr[x], adr[i]);
}
}
}
add(adr[x], {max(0ll, -v[x]), v[x]});
}
void solve()
{
ll n,s;
cin>>n>>s;
for (int i=1 ; i<=n ;i++)
{
cin>>v[i];
ll p;
cin>>p;
g[p].push_back(i);
g[i].push_back(p);
}
dfs(0);
ll old = s;
while (!pq[adr[0]].empty())
{
auto t = pq[adr[0]].top();
// cout<<t.first<<" "<<t.second<<"j"<<endl;
pq[adr[0]].pop();
if (t.first<=s)
s += t.second;
else
break;
}
cout<<s-old<<endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
ll tt = 1;
// cin>>tt;
while (tt--)
{
solve();
}
return 0;
}
