#include<bits/stdc++.h>
using namespace std;
#define int long long
#define F first
#define S second
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define pb push_back
#define sz(x) (int)(x.size())
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define vi vector<int>
#define vp vector<pii>
#define vvi vector<vi>
#define ykh mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count())
#define __lg(x) 63-__builtin_clzll(x)
#define pow2(x) (1LL<<x)
void __print(int x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
void setIO(string s) {
freopen((s + ".in").c_str(), "r", stdin);
freopen((s + ".out").c_str(), "w", stdout);
}
#ifdef local
void CHECK();
void setio(){
freopen("/Users/iantsai/cpp/input.txt","r",stdin);
freopen("/Users/iantsai/cpp/output.txt","w",stdout);
}
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
void setio(){}
#define debug(x...)
#endif
#define TOI_is_so_de ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);setio();
const int mxn = 3e5+5;
vector<int>adj[mxn];
int p[mxn], val[mxn];
bool vis[mxn];
#define pqpii priority_queue<pii>
pqpii dfs(int v){
pqpii pq;
for(auto u : adj[v]){
auto pq2 = dfs(u);
if(sz(pq2) > sz(pq))swap(pq, pq2);
while(sz(pq2)){
pq.push(pq2.top());
pq2.pop();
}
}
int mn = min(0LL,val[v]), sum = val[v];
while(sz(pq) and sum<=0){
auto [mn2, sum2] = pq.top();
pq.pop();
mn = min(mn, sum+mn2);
sum += sum2;
}
while(sz(pq)){
auto [mn2, sum2] = pq.top();
if(sum + mn2 < mn){
break;
}
pq.pop();
sum += sum2;
}
if(sum > 0){
pq.push({mn, sum});
}
return pq;
}
signed main(){
TOI_is_so_de;
int n, s, ans = 0;
cin >> n >> s;
val[0] = s;
for(int i=1;i<=n;i++){
cin >> val[i] >> p[i];
adj[p[i]].pb(i);
}
auto pq = dfs(0);
while(sz(pq)){
auto [mn, sum] = pq.top();
pq.pop();
if(ans + mn >= 0) ans += sum;
else break;
}
cout << ans-val[0] << '\n';
#ifdef local
CHECK();
#endif
}
/*
input:
*/
#ifdef local
void CHECK(){
cerr << "\n[Time]: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
function<bool(string,string)> compareFiles = [](string p1, string p2)->bool {
std::ifstream file1(p1);
std::ifstream file2(p2);
if (!file1.is_open() || !file2.is_open())return false;
std::string line1, line2;
while (getline(file1, line1) && getline(file2, line2)) {
if (line1 != line2)return false;
}
int cnta=0,cntb=0;
while(getline(file1,line1))cnta++;
while(getline(file2,line2))cntb++;
return cntb-cnta<=1;
};
bool check = compareFiles("output.txt","expected.txt");
if (check) cerr<<"ACCEPTED\n";
else cerr<<"WRONG ANSWER!\n";
}
#else
#endif
