#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long int
#define REP(i,n) for (int i = 1; i <= (n); i++)
#define fo(i,x,y) for (int i = (x); i <= (y); i++)
#define Redge(u) for (int k = head[u]; k != -1; k = edge[k].next)
using namespace std;
const int maxn = 1000005,maxm = 2000005,INF = 1000000000;
inline int read(){int out = 0,flag = 1;char c = getchar();while (c < 48 || c > 57) {if (c == '-') flag = -1; c = getchar();}while (c >= 48 && c <= 57) {out = out * 10 + c - 48; c = getchar();}return out * flag;
}
bool vis[maxn][2];
LL f[maxn][2],ans = 0;
int v[maxn],pre[maxn],n,head[maxn],nedge = 0,m = 0,cir[maxn][2];
struct EDGE{int to,next;}edge[maxm];
inline void build(int u,int v){edge[nedge] = (EDGE){v,head[u]}; head[u] = nedge++;edge[nedge] = (EDGE){u,head[v]}; head[v] = nedge++;
}
inline int find(int u){return u == pre[u] ? u : pre[u] = find(pre[u]);}
void dfs(int u,int p){vis[u][p] = true; f[u][1] = v[u]; f[u][0] = 0;int to;Redge(u)if (!vis[to = edge[k].to][p]){dfs(to,p);f[u][1] += f[to][0];f[u][0] += max(f[to][1],f[to][0]);}
}
int main()
{int to,fa,fb;n = read();REP(i,n) pre[i] = i,head[i] = -1;REP(i,n){v[i] = read(); to = read(); fa = find(i); fb = find(to); build(i,to);if (fa == fb) {cir[++m][0] = i; cir[m][1] = to;}else pre[fa] = fb;}REP(i,m){LL t = 0;dfs(cir[i][0],0); t = max(t,f[cir[i][0]][0]);dfs(cir[i][1],1); t = max(t,f[cir[i][1]][0]);ans += t;}cout << ans << endl;return 0;
}