#pragma GCC optimize("O1,O2,O3,Ofast,unroll-loops")
#include <bits/stdc++.h>
#include <string>
#include <iostream>
#include <cmath>
#include <numeric>
#include <stack>
#include <queue>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<vector<int>> vvi;
typedef vector<vector<pi>> vvpi;
typedef vector<ld> vd;
typedef vector<long long> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
#define FOR(i, a, b) for (ll i = a; i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)
#define uid(a, b) uniform_int_distribution<int>(a, b)(rng)
#define len(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define F first
#define nl endl
#define S second
#define lb lower_bound
#define ub upper_bound
#define aint(x) x.begin(), x.end()
#define raint(x) x.rbegin(), x.rend()
#define ins insert
const int MOD = 1e9+7;
void init(string name)
{
freopen((name + ".in").c_str(), "r", stdin);
freopen((name + ".out").c_str(), "w", stdout);
}
void fastIO()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
}
int N = 4e5;
vi used(N,0),profit(N,0), parent(N);
vvi sons(N,vi());
ll ans = 0;
vi roots;
void proc(int pos,ll money){
if(money < 0)return;
money += profit[pos];
if(money >= ans){
ans = max(money,ans);
}
for(int a:sons[pos]){
proc(a,money);
}
}
ll tmp_profit = 0,tmp_cost = 0;
void check(int pos,ll money,ll costtomx){
money += profit[pos];
costtomx = min(costtomx,money);
if(money >= tmp_profit){
tmp_cost = costtomx;
tmp_profit = max(money,tmp_profit);
}
for(int a:sons[pos]){
check(a,money,costtomx);
}
}
void solve()
{
ll n,s;cin >> n >> s;
ans = s;
FOR(i,0,n){
parent[i] = i;
ll a,b;cin >> a >> b;b--;
profit[i] = a;
parent[i] = b;
if(b != -1)sons[b].pb(i);
else roots.pb(i);
}
vector<pair<ll,pair<ll,int>>> to_proc;
for(int a:roots){
tmp_profit = 0,tmp_cost = 0;
check(a,0,0);
tmp_cost *= -1;
to_proc.pb({tmp_cost,{tmp_profit,a}});
}
sort(to_proc.begin(),to_proc.end());
for(auto a:to_proc){
proc(a.S.S,ans);
}
cout << ans-s << endl;
}
int main()
{
fastIO();
// init("test");
int t = 1;
// cin >> t;
while (t--)
solve();
return 0;
}
