#include <bits/stdc++.h>
using namespace std;
/*⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣤⠀⠀⠀⠀⠀⠀⠀⡄⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣤⣿⠛⣿⠀⠀⠀⠀⣤⣿⢻⡇⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣤⣿⡛⠀⣤⣿⣿⣤⣤⣿⣿⣤⢸⡇⠀
⠀⠀⠀⠀⠀⠀⠀⠀⣴⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⠀
⠀⠀⠀⠀⠀⠀⠀⣶⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡗⠀
⢠⣼⣿⣿⣿⣿⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷
⢸⣿⣿⡟⠛⠛⢿⣿⣿⣿⣿⣿⣿⣿⣤⣤⣤⣿⣿⣿⣿⣤⣤⣼⣿⣿
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⠛⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⠋
*/
#define fi first
#define se second
#define pb push_back
#define ins insert
#define sz(a) (int)(a.size())
#define all(x) (x).begin(),(x).end()
#define rep(i, a, b) for(int i = a; i < (b); ++i)
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}
#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
#include "debug.h"
#else
#define debug(...)
#endif
//const int mod = 1e9+7;
//const int mod = 998244353;
const int MAXN=3e5+5;
const ll inf=1e9,INF=1e18;
int n,x[MAXN],p[MAXN]; ll s;
vi g[MAXN]; ll ans = 0;
ll dfs(int v,int p = 0) {
ll sum = x[v];
for(int i : g[v]) {
if(i == p) continue;
sum += dfs(i,v);
}
return max(0ll,sum);
}
void solve(int tc = 0){
cin>>n>>s;
rep(i,1,n+1) {
cin>>x[i]>>p[i];
g[p[i]].pb(i);
}
rep(i,1,n+1) {
if(!p[i]) {
ans += dfs(i);
}
} print(ans);
}
signed main(){
ios_base::sync_with_stdio(false); cin.tie(0);
int tc=1;
//cin>>tc;
for(int t = 0; t < tc; t++) solve(t);
}
