1 /*
  2 ID:WULALA
  3 PROB:bzoj1040
  4 LANG:C++
  5 */
  6 #include <cstdio>
  7 #include <cstring>
  8 #include <algorithm>
  9 #include <cmath>
 10 #include <iostream>
 11 #include <fstream>
 12 #include <ctime>
 13 #define N 1000008
 14 #define M
 15 #define mod
 16 #define mid(l,r) ((l+r) >> 1)
 17 #define INF 0x7ffffff
 18 using namespace std;
 19
 20 int dfn[N],que,n,g[N],f[N],u,v,w[N],r,tot,ans,head[N],fa[N];
 21 bool vis[N];
 22
 23 struct WULALA
 24 {
 25     int node,next;
 26 }e[2*N];
 27
 28 void add(int x,int y)
 29 {
 30     e[++tot].node = y;
 31     e[tot].next = head[x];
 32     head[x] = tot;
 33     e[++tot].node = x;
 34     e[tot].next = head[y];
 35     head[y] = tot;
 36 }
 37
 38 void init()
 39 {
 40     scanf("%d",&n);
 41     for (int i = 1;i <= n;i++)
 42     {
 43         int b;
 44         scanf("%d%d",&w[i],&b);
 45         add(i,b);
 46     }
 47 }
 48
 49 void find_cir(int a)
 50 {
 51     vis[a] = true;
 52     int c = head[a];
 53     while(c)
 54     {
 55         if (e[c].node == fa[a])
 56             {c = e[c].next; continue;}
 57         if (vis[e[c].node])
 58         {
 59             u = e[c].node;
 60             v = a;
 61         }
 62         else
 63         {
 64             fa[e[c].node] = a;
 65             find_cir(e[c].node);
 66         }
 67         c = e[c].next;
 68     }
 69 }
 70
 71 int dfs(int a,int m)
 72 {
 73     if (m != v) f[a] = w[a];
 74     int c = head[a];
 75     while(c)
 76     {
 77         if (e[c].node == fa[a]||e[c].node == u)
 78         {c = e[c].next; continue;}
 79         fa[e[c].node] = a;
 80         dfs(e[c].node,m);
 81         g[a] += max(g[e[c].node],f[e[c].node]);
 82         f[a] += g[e[c].node];
 83         c = e[c].next;
 84     }
 85     if (a == u)
 86     {
 87         if (m == u) return g[u];
 88         return (max(g[u],f[u]));
 89     }
 90 }
 91
 92 void work(int a)
 93 {
 94     int r;
 95     memset(f,0,sizeof(f));
 96     memset(g,0,sizeof(g));
 97     memset(fa,0,sizeof(fa));
 98     find_cir(a);
 99     memset(fa,0,sizeof(fa));
100     memset(f,0,sizeof(f));
101     memset(g,0,sizeof(g));
102     fa[u] = v;
103     r = dfs(u,v);
104     memset(f,0,sizeof(f));
105     memset(g,0,sizeof(g));
106     r = max(r,dfs(u,u));
107     ans += r;
108 }
109
110 int main()
111 {
112     init();
113     for (int i = 1;i <= n;i++)
114         if (!vis[i]) work(i);
115     printf("%d\n",ans);
116     return 0;
117 }