#pragma GCC optimize("O1,O2,O3,Ofast,unroll-loops")
#include <bits/stdc++.h>
#include <string>
#include <iostream>
#include <cmath>
#include <numeric>
#include <stack>
#include <queue>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<vector<int>> vvi;
typedef vector<vector<pi>> vvpi;
typedef vector<ld> vd;
typedef vector<long long> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
#define FOR(i, a, b) for (ll i = a; i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)
#define uid(a, b) uniform_int_distribution<int>(a, b)(rng)
#define len(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define F first
#define nl endl
#define S second
#define lb lower_bound
#define ub upper_bound
#define aint(x) x.begin(), x.end()
#define raint(x) x.rbegin(), x.rend()
#define ins insert
const int MOD = 1e9+7;
void init(string name)
{
freopen((name + ".in").c_str(), "r", stdin);
freopen((name + ".out").c_str(), "w", stdout);
}
void fastIO()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
}
int N = 3e5+20;
vi parent (N,0);
vector<set<int>> sons(N, set<int>());
queue<int> roots;
vl profit(N,0);
ll ans = 0;
int used = 0;
void proc(int pos,ll money,set<int> pathset,vi path){
if(used)return;
money += profit[pos];
pathset.insert(pos);
path.pb(pos);
// cout << pos << " " << money << " " << ans << endl;
if(money > ans){
ans = money;
for(int b:path){
// cout << b << " -> ";
for(int a:sons[b]){
if(pathset.count(a) == 0){
// cout << a << " ";
roots.push(a);
}
}
// cout << endl;
// sons[b].clear();
}
// cout << "ans - " << ans << " " << roots.size()<< endl;
used = 1;
return;
}
// cout << "C" << endl;
for(int a:sons[pos]){
proc(a,money,pathset,path);
}
}
void solve()
{
int n;ll s;cin >> n >> s;
FOR(i,0,n){
ll a;int b;cin >> a >> b;
b --;
if(b == -1){
roots.push(i);
}else{
parent[i] = b;
sons[b].insert(i);
}
profit[i] = a;
}
// FOR(i,0,n){
// cout << i << " -> ";
// for(int a:sons[i])cout << a << " ";
// cout << endl;
// }
while(!roots.empty()){
used = 0;
// cout << "B" << endl;
int a = roots.front();roots.pop();
set<int> pathset;vi path;
proc(a,ans,pathset,path);
// cout << "A" << endl;
}
cout << ans << endl;
}
int main()
{
fastIO();
// init("test");
int t = 1;
// cin >> t;
while (t--)
solve();
return 0;
}
