#include<bits/stdc++.h>
using namespace std;
#define LL long long
const int N = 1e6 + 10;
struct edge{int v, ne;}e[N];
int n,h[N],w[N],idx;
int r1,r2,vis[N];
LL f[N][2],sum;

void add(int a,int b){
	e[++idx]={b,h[a]};
	h[a]=idx;
}

void find(int u,int rt){//找两个根
	vis[u]=1;
	for(int i=h[u];i;i=e[i].ne){
		int v=e[i].v;
		if(v==rt){
			r1=u,r2=v;
			return;
		}
		if(vis[v])continue;
		find(v,rt);
	}
}

LL dfs(int u,int rt){//树上DP
	f[u][0]=0; f[u][1]=w[u];
	for(int i=h[u];i;i=e[i].ne){
		int v=e[i].v;
		if(v==rt)continue;
		dfs(v,rt);
		f[u][0]+=max(f[v][1],f[v][0]);
		f[u][1]+=f[v][0];
	}
	return f[u][0];
}

int main(){
	scanf("%d",&n);
	for(int v=1,u;v<=n;v++)
		scanf("%d%d",&w[v],&u),add(u,v);
	for(int i=1;i<=n;i++)
		if(!vis[i]){
			r1=r2=0;
			find(i,i);
			if(r1){
				LL res1=dfs(r1,r1);
				LL res2=dfs(r2,r2);
				sum+=max(res1,res2);			
			}
		}
	printf("%lld",sum);
	return 0;
}

if(r1){

LL res1=dfs(r1,r1);
LL res2=dfs(r2,r2);
sum+=max(res1,res2);			

}