#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define len(x) (ll) x.size()
#define all(x) x.begin(), x.end()
using namespace std;
typedef long long ll;
const int N = 3e5 + 11;
const ll inf = 2e18 + 12;
ll n, s, prf;
ll p[N], a[N], rt[N];
vector < ll > g[N];
struct node{
ll r, p;
bool operator >(const node &x) const {
if(r == x.r) return p > x.p;
else return r > x.r;
}
};
priority_queue < node, vector < node >, greater < node > > q[N];
ll mrg(ll x, ll y){
if(len(q[x]) < len(q[y])) swap(x, y);
while(len(q[y])) q[x].push(q[y].top()), q[y].pop();
return x;
}
void cmb(ll v, node x){
while(len(q[v])){
node u = q[v].top();
if(x.p <= 0) q[v].pop(), x = {max(x.r, u.r - x.p), u.p + x.p};
else{
if(x.r > u.r) q[v].pop(), x = {x.r, u.p + x.p};
else{
q[v].push(x);
break;
}
}
}
if(q[v].empty()) q[v].push(x);
if(len(q[v]) == 1 && q[v].top().p <= 0) q[v].pop();
}
void dfs(ll v){
if(g[v].empty()) rt[v] = v;
for(ll u : g[v]){
dfs(u);
if(!rt[v]) rt[v] = rt[u];
else rt[v] = mrg(rt[v], rt[u]);
}
cmb(rt[v], {max(0ll, -a[v]), a[v]});
}
signed main(){
cin >> n >> s, prf = s;
for(ll i = 1; i <= n; i++) cin >> a[i] >> p[i], g[p[i]].pb(i);
dfs(0);
ll v = rt[0];
while(len(q[v])){
if(prf >= q[v].top().r) prf += q[v].top().p;
q[v].pop();
}
cout << prf - s;
}
