#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
const int inf = 1e18;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> p2;
#define rep(i, high) for (int i = 0; i < (high); i++)
#define repp(i, lo, high) for (int i = (lo); i < (high); i++)
#define repe(i, container) for (auto& i : container)
#define sz(x) ((int)(x).size())
#define all(x) begin(x), end(x)
map<int, int> dp(int u, vvi & adj, vi & value)
{
map<int, int> ret;
repe(e, adj[u])
{
map<int, int> c = dp(e, adj, value);
repe(u, c) ret[u.first] += u.second;
}
int v = value[u];
if (v>=0)
{
ret[0] += v;
}
else
{
int s = -v;
int moneys = 0;
while (sz(ret) && (begin(ret)->first <= s))
{
s += begin(ret)->first - moneys;
moneys += begin(ret)->second;
ret.erase(ret.begin());
}
moneys += v;
if (moneys>0)
{
ret[s] += moneys;
}
}
return ret;
}
signed main()
{
cin.tie(0)->sync_with_stdio(0);
int n, s;
cin >> n >> s;
vi nodevalue(n+1);
vvi adj(n+1);
vi roots;
rep(i, n)
{
int p, v;
cin >> v >> p;
nodevalue[i+1] = v;
adj[p].push_back(i+1);
}
int moneys = s;
repe(s, dp(0, adj, nodevalue))
{
if (moneys>=s.first)
{
moneys += s.second;
}
}
cout << moneys-s;
return 0;
}
