#include<bits/stdc++.h>
#define int long long
using namespace std;
#define fi first
#define sc second
#define pii pair<int,int>
#define pb push_back
#define umap unordered_map
#define mset multiset
#define pq priority_queue
const int maxn=3e5+10;
struct node{
int u,w;
bool operator <(node _) const{
return w<_.w;
}
};
int n,s,val[maxn],in[maxn],dp[maxn];
vector<int> g[maxn];
pq<node> q;
void solve(){
cin>>n>>s;
for(int i=1,x;i<=n;i++){
cin>>val[i]>>x;
if(x) g[x].pb(i),in[i]++;
}
int res=s;
for(int i=1;i<=n;i++) if(!in[i]) q.push({i,val[i]});
while(q.size()){
int u=q.top().u,w=q.top().w;
q.pop();
if(s+w<0) continue;
s+=w,res=max(res,s);
for(int v:g[u]){
in[v]--;
if(!in[v]) q.push({v,val[v]});
}
}
cout<<res<<endl;
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(0),cout.tie(0);
int t=1;
// cin>>t;
while(t--) solve();
return 0;
}
/*
Samples
input:
output:
THINGS TODO:
检查freopen，尤其是后缀名
检查空间
检查调试语句是否全部注释
*/
