#include <bits/stdc++.h>
using namespace std;
// thank you geothermal :goat:
void __deb(int t) {cerr << t;}
void __deb(long t) {cerr << t;}
void __deb(long long t) {cerr << t;}
void __deb(unsigned int t) {cerr << t;}
void __deb(unsigned long t) {cerr << t;}
void __deb(unsigned long long t) {cerr << t;}
void __deb(float t) {cerr << t;}
void __deb(double t) {cerr << t;}
void __deb(long double t) {cerr << t;}
void __deb(char t) {cerr << '\'' << t << '\'';}
void __deb(const char *t) {cerr << '\"' << t << '\"';}
void __deb(const string &t) {cerr << '\"' << t << '\"';}
void __deb(bool t) {cerr << (t ? "true" : "false");}
template<typename T, typename V>
void __deb(const pair<T, V> &x){ cerr << '{'; __deb(x.first); cerr << ", "; __deb(x.second); cerr << '}'; }
template<typename T>
void __deb(const T &x){
int f = 0; cerr << '{';
for(auto &i: x){ if(f++) cerr << ", "; __deb(i);}
cerr << "}";
}
void _rdeb(vector<string> &names, int ind){}
template<typename T, typename... V>
void _rdeb(vector<string> &names, int ind, T t, V... v){
if(ind != 0) cerr << "==============\n";
cerr << names[ind] << '\n'; __deb(t); cerr << '\n';
_rdeb(names, ind+1, v...);
}
template<typename... V>
void _deb(string vars, V... v){
vector<string> names(1); int in{};
for(char c : vars)
if(c == ',' && in == 0){
while(names.back().size() && isspace(names.back().back())) names.back().pop_back();
names.push_back("");
}else{
if(c == '(') in++; if(c == ')') in--;
if(!isspace(c) || names.back().size()) names.back().push_back(c);
}
while(names.back().size() && isspace(names.back().back())) names.back().pop_back();
_rdeb(names, 0, v...);
}
#ifdef DEBUG
#define deb(x...) { \
cerr << __func__ << ':' << __LINE__ << '\n'; \
_deb(#x, x); \
cerr << '\n'; \
}
#define debsep(x...) { \
cerr << __func__ << ':' << __LINE__ << '\n'; \
_deb(#x, x); \
cerr << "****************************\n"; \
}
#else
#define deb(x...)
#define debsep(x...)
#endif
#define ar array
#define ll long long
typedef int uci;
#define int long long
#define F first
#define S second
typedef complex<double> cd;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define irep(i, a, b) for(int i = a; i > (b); --i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
#define ve vector
typedef ve<int> vi;
typedef ve<vi> vvi;
seed_seq seq{
(uint64_t) chrono::duration_cast<chrono::nanoseconds>(chrono::high_resolution_clock::now().time_since_epoch()).count(),
(uint64_t) __builtin_ia32_rdtsc(),
(uint64_t) (uintptr_t) make_unique<char>().get()
};
mt19937 rng(seq);
// mt19937_64 lrng(seq);
struct debugger{
template <typename T>
debugger& operator<<(T &a){
#ifdef DEBUG
cerr << a;
#endif
return *this;
}
template <typename T>
debugger& operator<<(T &&a){
#ifdef DEBUG
cerr << a;
#endif
return *this;
}
} deb;
const double PI = acos(-1.0);
const int MAXN = 3e5 + 1;
const int MOD = 1e9 + 7;
const int INF = 1e9;
const ll LINF = 1e18;
//! function insert
//THINK FIRST, CODE SECOND
//DON'T GET STUCK ON ONE STRATEGY
//CALM DOWNNN FOR ONCE IN YOUR LIFE
//REDUCE
//COUGH E??!?!?!! O.O
//uwu i see you ryan
int wws[MAXN];
priority_queue<ar<int, 2>, ve<ar<int, 2>>, greater<>> vals[MAXN];
void dfs(int v, vvi &adj){
for(int i : adj[v]){
dfs(i, adj);
if(sz(vals[i]) > sz(vals[v])){
vals[v].swap(vals[i]);
}
while(sz(vals[i])){
vals[v].push(vals[i].top());
vals[i].pop();
}
}
ar<int, 2> cur = {max(0ll, -wws[v]), wws[v]};
while(sz(vals[v])){
ar<int, 2> t = vals[v].top();
if(cur[1] <= 0){
vals[v].pop();
cur[0] = max(cur[0], t[0] - cur[1]);
cur[1] += t[1];
}else{
if(cur[0] < t[0]){
vals[v].push(cur);
cur[1] = -1;
break;
}else{
vals[v].pop();
cur[1] += t[1];
}
}
}
if(sz(vals[v]) == 0 && cur[1] > 0)
vals[v].push(cur);
}
void solve() {
int n, s;
cin >> n >> s;
vvi adj(n);
vi ins(n);
rep(i, 0, n){
int x, p;
cin >> x >> p;
wws[i] = x;
if(p != 0){
ins[i]++;
adj[p-1].push_back(i);
}
}
priority_queue<ar<int, 2>, ve<ar<int, 2>>, greater<>> q;
rep(i, 0, n){
if(ins[i] == 0){
dfs(i, adj);
while(sz(vals[i])){
q.push(vals[i].top());
vals[i].pop();
}
}
}
int lim = s;
while(sz(q) && q.top()[0] <= lim){
lim += q.top()[1];
q.pop();
}
cout << lim-s << '\n';
}
uci main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
// cout << "Case #" << t << ": ";
solve();
}
/*
random number generator stuff
num = rng(); gives integer number
num = uniform_int_distribution<int>(a, b)(rng); -> bounds [a, b]
num = uniform_real_distribution<double>(a, b)(rng); -> bounds [a, b)
can also instantiate distributions and call on generator:
uniform_int_distribution<int> thing(a, b);
num = thing(rng);
*/
// struct custom_hash {
// static uint64_t splitmix64(uint64_t x) {
// // http://xorshift.di.unimi.it/splitmix64.c
// x += 0x9e3779b97f4a7c15;
// x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
// x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
// return x ^ (x >> 31);
// }
// size_t operator()(uint64_t x) const {
// static const uint64_t FIXED_RANDOM = lrng();
// return splitmix64(x + FIXED_RANDOM);
// }
// };
