RT，WA+TLE，30pts

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
typedef pair<pair<ll,ll>,ll> P3;
typedef pair<pair<ll,ll>,pair<ll,ll> >P4;
#define mkp make_pair
#define fi first
#define se second
// #define FastIO
// #define OIcontest
const ll mod=998244353;
const ll maxn=500005;

inline ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-') f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=getchar();
    return x*f;
}
inline ll maxx(ll a,ll b){ return a>b?a:b; }
inline ll minn(ll a,ll b){ return a<b?a:b; }
inline ll lowbit(ll x){ return x&-x; }
/*--------------head------------------*/
ll n,con[1000005];
struct Edge{
    ll to,nxt;
}edge[1000005];
ll head[1000005],tot;
void add(ll u,ll v){
    edge[++tot].to=v;
    edge[tot].nxt=head[u];
    head[u]=tot;
}
ll huan[1000005], hd=1, tp, vis[1000005], vis2[1000005],End;
ll link[1000005], tl;
void dfs(ll x){
    if(End) return;
    huan[++tp]=x;
    for(ll i=head[x];i;i=edge[i].nxt){
        ll y=edge[i].to;
        if(End) return;
        if(vis[y]){
            End=1;
            while(huan[hd]!=y) hd++;
            return;
        }
        vis[y]=1;
        if(End) return;
        dfs(y);
        if(End) return;
    }
    tp--;
}
ll dp[1000005][2], f[1000005][2];
void treedp(ll x){
    dp[x][1]=con[x];
    for(ll i=head[x];i;i=edge[i].nxt){
        ll y=edge[i].to;
        if(vis2[y]) continue;
        treedp(y);
        dp[x][1]+=dp[y][0];
        dp[x][0]+=max(dp[y][0],dp[y][1]);
    }
}
ll answer=0;
void doit(){
    ll ans=0;
    for(ll i=1;i<=tl;i++) vis2[link[i]]=1;
    for(ll i=1;i<=tl;i++) treedp(link[i]);
    for(ll i=1;i<=tl;i++){
        f[i][0]=dp[link[i]][0]+max(f[i-1][0],f[i-1][1]);
        f[i][1]=dp[link[i]][1]+f[i-1][0];
    }
    ans=f[tl][0];
    f[1][1]=-1e18;
    for(ll i=2;i<=tl;i++){
        f[i][0]=dp[link[i]][0]+max(f[i-1][0],f[i-1][1]);
        f[i][1]=dp[link[i]][1]+f[i-1][0];
    }
    ans=max(ans,max(f[tl][0],f[tl][1]));
    answer+=ans;
}
void solve(){
    n=read();
    for(ll i=1,fa;i<=n;i++){
        con[i]=read(), fa=read();
        add(fa,i);
    }
    for(ll i=1;i<=n;i++){
        if(!vis[i]){
            vis[i]=1;hd=1, tp=0, tl=0;
            dfs(i);
            End=0;
            for(ll i=hd;i<=tp;i++) link[++tl]=huan[i];
            doit();
        }
    }
    cout<<answer<<endl;
}
int main(){
    #ifdef OIcontest
        freopen(".in","r",stdin);
        freopen(".out","w",stdout);
    #endif
    #ifndef FastIO
        ios::sync_with_stdio(0); cin.tie(0), cout.tie(0);
    #endif
    ll T=1;
    while(T--) solve();
    return 0;
}
/*
是谁挥霍的时光啊，是谁苦苦的奢望啊

这不是一个问题，也不需要你的回答

No answer. 
*/