#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair <ll,ll> pll;
typedef pair <int,int> pii;
typedef pair <int,pii> piii;
#define forr(_a,_b,_c) for(int _a = (_b); _a <= int (_c); ++_a)
#define ford(_a,_b,_c) for(int _a = (_b) + 1; _a --> int (_c);)
#define forf(_a,_b,_c) for(int _a = (_b); _a < int (_c); ++_a)
#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define all(x) begin(x),end(x)
#define mask(i) (1LL << (i))
#define bit(x, i) (((x) >> (i)) & 1)
#define bp __builtin_popcountll
#define file "test"
template<class X, class Y>
bool minz(X &x, const Y &y) {
if (x > y) {
x = y;
return true;
} return false;
}
template<class X, class Y>
bool maxz(X &x, const Y &y) {
if (x < y) {
x = y;
return true;
} return false;
}
const int N = 5e5 + 5;
const ll oo = (ll) 1e18;
const ll mod = 1e9 + 7; // 998244353;
ll ans, p[N], f[N], w[N], dp[N], del[N], s, n;
vector <int> a[N];
ll dfs1 (int u){
ll tmp = w[u];
for (int v : a[u])
tmp += dfs1(v);
return max(0ll, tmp);
}
stack <int> st;
void dfs (int u){
f[u] += w[u];
if (ans + s + f[u] < 0){
return;
}
dp[u] = w[u];
st.push(u);
for (int v : a[u]){
if (del[v]) continue;
f[v] = f[u];
dfs(v);
dp[u] += dp[v];
}
if (dp[u] < 0){
dp[u] = 0;
while (st.top() != u){
st.pop();
}
st.pop();
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef kaguya
freopen(file".inp", "r", stdin); freopen(file".out", "w", stdout);
#endif
cin >> n >> s;
forr (i, 1, n){
cin >> w[i] >> p[i];
a[p[i]].pb(i);
}
if (s == oo){
forr (i, 1, n)
if (!p[i]){
ans += dfs1(i);
}
cout << ans << "\n";
} else if (n <= 5000){
forr (t, 1, n){
forr (i, 1, n){
dp[i] = f[i] = 0;
}
forr (i, 1, n){
if (!p[i] && !del[i]){
dfs(i);
while (st.size()){
int u = st.top();
st.pop();
del[u] = 1;
ans += w[u];
for (int v : a[u]){
p[v] = 0;
}
}
}
}
}
cout << ans << "\n";
}
return 0;
}
/*
*/
