#include<bits/stdc++.h>
using namespace std;
#ifdef DEBUG
auto& operator <<(auto& o, pair<auto, auto> p) {return o<<"{"<<p.first<<", "<<p.second<<"}";}
auto& operator <<(auto& o, auto x) {o<<"{"; for(auto v : x) o<<v<<", "; return o<<"}";}
#define debug(X) cerr<<"["#X"]: "<<X<<endl;
#else
#define debug(X) {}
#endif
#define int long long
const int INF = numeric_limits<int>::max();
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, s;
cin>>n>>s;
int org = s;
vector<vector<int> > graph(n+1);
vector<int> cost(n+1);
for(int i=1;i<=n;i++)
{
int p, c;
cin>>c>>p;
graph[p].push_back(i);
cost[i] = c;
}
vector<pair<int, int> > dp(n+1);
function<void(int, int)> dfs = [&](int a, int par)
{
vector<pair<int, int> > sons;
for(auto v : graph[a])
if(v != par)
{
dfs(v, a);
sons.push_back(dp[v]);
}
sort(sons.begin(), sons.end());
int k = -1, c = cost[a];
while(c < 0 && k != (int)sons.size()-1) {k++; c += sons[k].second;}
if(c < 0) {dp[a] = {INF, -INF}; return;}
int minS = 0;
int pref = 0;
for(int i=0;i<=k;i++) {minS = max(minS, sons[i].first - pref); pref += sons[i].second;}
minS -= cost[a];
dp[a] = {minS, pref + cost[a]};
return;
};
dfs(0, -1);
priority_queue<pair<int, int> > q;
q.push({0, 0});
while(!q.empty())
{
auto a = q.top();
debug(a);
q.pop();
if(-a.first > s) break;
s += cost[a.second];
for(auto v : graph[a.second]) q.push({-dp[v].first, v});
}
cout<<s-org;
}
