#include <bits/stdc++.h>
#define sz(x) ((int)x.size())
#define all(x) x.begin(), x.end()
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using namespace std;
const int N = 3e5 + 42;
struct Node {
i64 i, sub, add, gain;
bool operator <(const Node& other) const {
if(max(sub, other.sub - gain) == max(other.sub, sub - other.gain)) {
if(gain == other.gain)
return i < other.i;
return gain > other.gain;
}
return max(sub, other.sub - gain) < max(other.sub, sub - other.gain);
}
};
int par[N];
int F(int i) {
if(par[i] == i) return i;
return par[i] = F(par[i]);
}
void U(int a, int b) {
a = F(a), b = F(b);
par[b] = a;
}
Node merge(Node a, Node b) {
Node ans;
ans.i = a.i;
ans.sub = max(a.sub, b.sub - a.gain);
ans.gain = a.gain + b.gain;
ans.add = ans.gain + ans.sub;
return ans;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n; cin >> n;
i64 s; cin >> s;
set<Node> pq;
vector<int> p(n+1);
vector<Node> node(n+1);
for(int i = 1; i <= n; i++) {
node[i].i = i;
par[i] = i;
i64 x; cin >> x >> p[i];
node[i].gain = x;
if(x < 0) {
node[i].sub = -x, node[i].add = 0;
} else {
node[i].add = x, node[i].sub = 0;
}
pq.insert(node[i]);
}
while(!pq.empty()) {
auto it = pq.begin();
Node x = *it;
Node fus = merge(node[F(p[x.i])], x);
if(!(F(p[x.i]) == 0 && (fus.sub > s || x.gain < 0))) {
U(p[x.i], x.i);
pq.erase(it);
if(F(p[x.i]) != 0) {
pq.erase(node[F(p[x.i])]);
pq.insert(fus);
}
node[F(p[x.i])] = fus;
} else {
pq.erase(it);
}
}
cout << max(0ll, node[0].gain) << '\n';
}
