/* Author : Mychecksdead */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
#define ff first
#define ss second
#define pii pair<int,int>
#define vi vector<int>
const int N = 1e6+100, M = 1e5+10, K = 52, MX = 30;
int n; ll s, a[N], dp[N], sum[N];
vector<int> g[N], R;
vector<pair<ll, ll>> T[N];
void dfs(int v){
dp[v] = a[v];
sum[v] = a[v];
priority_queue<array<ll, 3>> Q;
for(int u: g[v]){
dfs(u);
if(sum[u] >= 0){
Q.push({
dp[u], a[u], u
});
}
// for(auto p: T[u]) T[v].pb(p);
}
while(!Q.empty() && sum[v] < 0){
auto p = Q.top(); Q.pop();
sum[v] += p[1];
dp[v] = min(dp[v], sum[v]);
for(int u: g[p[2]]){
if(sum[u] >= 0)
Q.push({dp[u], a[u], u});
}
}
// for(int i = 0; i < T[v].size() && sum < 0; ++i){
// sum += T[v][i].ss;
// dp[v] = min(dp[v], sum);
// }
// if(sum >= 0){
// T[v].pb({-dp[v], a[v]});
// }
// cout << v << ' ' << dp[v] << '\n';
}
void solve(){
cin >> n >> s;
for(int i = 1; i <= n; ++i){
cin >> a[i];
int p; cin >> p;
g[p].pb(i);
if(p==0) R.pb(i);
}
priority_queue<array<ll, 3>> Q;
for(int r: R){
dfs(r);
if(sum[r] >= 0){
Q.push({
dp[r], a[r], r
});
}
// for(auto p: T[u]) T[v].pb(p);
}
ll ans = s, cur = s;
while(!Q.empty()){
auto p = Q.top(); Q.pop();
if(cur + p[1] < 0) break;
// cout << p[2] << ' ';
cur += p[1];
ans=max(ans, cur);
for(int u: g[p[2]]){
if(sum[u] >= 0){
Q.push({dp[u], a[u], u});
}
}
}
cout << ans - s;
}
int main(){
cin.tie(0); ios::sync_with_stdio(0);
int tt = 1, aa;
// freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
while(tt--){
solve();
en;
}
cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
return 0;
}
