#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1ULL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(abs(a), abs(b));}
ll lcm(ll a, ll b){return abs(a) / gcd(a, b) * abs(b);}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ull mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const int N = 3e5 + 69;
int n; ll s;
vector<int> graph[N];
int p[N];
ll a[N];
vector<pair<ll,ll>> dp[N];
void nigger_melon(vector<pair<ll, ll>> &v){
vector<pair<ll, ll>> tmp;
for(auto i: v){
if (tmp.size() == 0 || tmp.back().first + tmp.back().second < i.first) {
tmp.push_back(i);
}
else tmp.back().second += i.second;
}
v = tmp;
}
void dfs(int u){
for(int v: graph[u]) {
dfs(v);
for(auto i: dp[v]) dp[u].push_back(i);
}
sort(ALL(dp[u]));
if (a[u] > 0){
dp[u].insert(dp[u].begin(), make_pair(0, a[u]));
}
else{
vector<pair<ll, ll>> tmp;
ll sum = a[u];
for(auto i: dp[u]){
i.first -= a[u];
sum += i.second;
if (sum > 0){
tmp.push_back(make_pair(i.first, sum));
sum = 0;
}
}
dp[u] = tmp;
}
nigger_melon(dp[u]);
// cout << "Node: " << u << "\n";
// for(auto i: dp[u]) cout << i.first << " " << i.second << "\n";
}
void solve(){
cin >> n >> s;
for(int i = 1; i <= n; ++i) {
cin >> a[i] >> p[i];
graph[p[i]].push_back(i);
}
dfs(0);
ll t = s;
for(auto i: dp[0]){
if (t >= i.first) t += i.second;
}
cout << t - s << "\n";
}
int main(void){
ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
clock_t start = clock();
solve();
cerr << "Time elapsed: " << clock() - start << "ms!\n";
return 0;
}
