1 #include<iostream>
2 #include<cstdio>
3 #include<cstring>
4 #include<cstdlib>
5 #include<algorithm>
6 using namespace std;
7 const int maxn=2e6+10;
8 long long dp[maxn][2];
9 long long w[maxn];
10
11 struct node
12 {
13 long long to,next,value;
14 }way[maxn];
15 long long tmp;
16 long long tot;
17 long long n,x;
18 long long head[maxn];
19 bool vis[maxn];
20 long long root;
21 long long father;
22 long long ans1,ans;
23 int read()
24 {
25 int flag = 1;
26 char c = getchar();
27 while ((!isdigit(c)) && c != '-') c = getchar();
28 if (c == '-') flag = -1, c = getchar();
29 int init = c & 15;
30 while (isdigit(c = getchar())) init = (init << 3) + (init << 1) + (c & 15);
31 return init * flag;
32 }
33 void add(long long x,long long y,long long w)
34 {
35 way[++tot].next=head[x];
36 way[tot].to=y;
37 way[tot].value=w;
38 head[x]=tot;
39 }
40 void dfs(long long x,long long fa)
41 {
42 vis[x]=1;
43 for(int i=head[x];i;i=way[i].next)
44 {
45 long long to=way[i].to;
46 if(to==fa)
47 {
48 continue;
49 }
50 if(vis[to])
51 {
52 root=to;
53 father=x;
54 tmp=way[i].value;
55 }
56 else
57 {
58 dfs(to,x);
59 }
60 }
61 }
62 void shu_dp(long long x,long long fa)
63 {
64 dp[x][0]=0;
65 dp[x][1]=w[x];
66 for(int i=head[x];i;i=way[i].next)
67 {
68 long long to=way[i].to;
69 if(way[i].value==tmp||to==fa)
70 {
71 continue;
72 }
73 shu_dp(to,x);
74 dp[x][0]+=max(dp[to][0],dp[to][1]);
75 dp[x][1]+=dp[to][0];
76 }
77 }
78 int main()
79 {
80 n=read();
81 for(int i=1;i<=n;i++)
82 {
83 w[i]=read();
84 x=read();
85 add(i,x,i);
86 add(x,i,i);
87 }
88 for(int i=1;i<=n;i++)
89 {
90 if(!vis[i])
91 {
92 dfs(i,0);
93 shu_dp(root,0);
94 ans1=dp[root][0];
95 shu_dp(father,0);
96 long long ans2;
97 ans2=dp[father][0];
98 ans1=max(ans1,ans2);
99 ans+=ans1;
100 }
101 }
102 printf("%lld\n",ans);
103 return 0;
104 }
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