#include <bits/stdc++.h>
using namespace std;
void __print(int x){cerr << x;}
void __print(long long x){cerr << x;}
void __print(string x){cerr << "\"" << x << "\"";}
void __print(char x){cerr << "\'" << x << "\'";}
template<typename T, typename V>
void __print(pair<T, V>x){
cerr << "{"; __print(x.first); cerr << ", "; __print(x.second); cerr << "}";
}
template<typename T>
void __print(T t){
cerr << "{"; int f =0;
for (auto i: t) {
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...);
}
#ifdef LOCAL
#define debug(x...) cerr << "[" << #x << "] = [", _print(x)
#else
#define debug(x...)
#endif
#define int long long
typedef pair<int, int> T;
const int oo = 1e18, oo2 = 1e9+7;
void solve(){
int n, s; cin >> n >> s;
vector<int>a(n+1), to(n+1);
vector<vector<int>>g(n+1);
for (int i = 1; i<=n; i++){
cin >> a[i] >> to[i];
g[to[i]].emplace_back(i);
debug(to[i], i);
}
vector<int>vis(n+1), dp(n+1);
function<void(int)>dfessa =[&](int v){
for (auto x: g[v]){
dp[x] = dp[v] + a[x];
dfessa(x);
}
};
dfessa(0);
debug(dp);
vis.assign(n+1, 0);
vis[0] = 1;
function<void(int, int)>sub = [&](int v, int ile){
dp[v] -= ile;
for (auto x: g[v]) sub(x, ile);
};
int ans = 0;
while (1){
T mx = {-oo, -oo};
vector<int>ok(n+1);
ok[0] = 1;
function<void(int)>check = [&](int v){
if (dp[v] < -s && dp[v] > -oo) return;
ok[v] = 1;
for (auto x: g[v]){
check(x);
}
};
check(0);
debug(ok);
for (int i = 1; i<=n; i++){
if (ok[i]) {
mx = max(mx, T{dp[i], i});
}
}
if (mx.first <= 0) break;
ans += mx.first;
s += mx.first;
debug(mx);
int v = mx.second;
int prev = -1;
while (!vis[v]){
vis[v] = 1;
for (auto x: g[v]){
if (x != prev){
sub(x, dp[v]);
}
}
dp[v] = -oo;
prev = v;
v = to[v];
}
debug(dp);
}
cout << ans << "\n";
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
solve();
return 0;
}
