#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
const int LIM = 1e6;
pair<int, int> adj[LIM + 1][3] = {};
vector<int> cycle, cycle_weight, st, weight;
bitset<LIM + 1> part_of_cycle, vis, vis_cycle, length_two_cycle;
void add_edge(int u, int v, int w) {
if(adj[u][0].first == 0) {
adj[u][0] = make_pair(v, w);
}
else if(adj[u][1].first == 0) {
adj[u][1] = make_pair(v, w);
}
else {
adj[u][2] = make_pair(v, w);
}
}
bool dfs_cycle(int cur, int par = -1, int last_weight = 0) {
vis[cur] = 1;
vis_cycle[cur] = 1;
st.push_back(cur); weight.push_back(last_weight);
for(int it = 0; it < 3; ++it) {
if(adj[cur][it].first == 0)break;
if(adj[cur][it].first == par) {
if(length_two_cycle[cur] && length_two_cycle[par]) {
cycle.push_back(st.back()); cycle_weight.push_back(weight.back()); part_of_cycle[st.back()] = 1;
cycle.push_back(adj[cur][it].first); cycle_weight.push_back(adj[cur][it].second); part_of_cycle[adj[cur][it].first] = 1;
return 1;
}
continue;
}
if(!vis[adj[cur][it].first]) {
if(dfs_cycle(adj[cur][it].first, cur, adj[cur][it].second)) {
return 1;
}
}
else if(vis_cycle[adj[cur][it].first]) {
while(st.back() != adj[cur][it].first) {
cycle.push_back(st.back()); cycle_weight.push_back(weight.back());
part_of_cycle[st.back()] = 1;
st.pop_back(); weight.pop_back();
}
part_of_cycle[adj[cur][it].first] = 1;
cycle.push_back(adj[cur][it].first); cycle_weight.push_back(adj[cur][it].second);
return 1;
}
}
st.pop_back(); weight.pop_back();
vis_cycle[cur] = 0;
return 0;
}
ll max_length = 0;
ll dfs(int cur, int par = -1, int last_weight = 0) {
vis[cur] = 1;
ll first_max = 0, second_max = 0;
for(int it = 0; it < 3; ++it) {
if(adj[cur][it].first == 0)break;
if(part_of_cycle[adj[cur][it].first] || adj[cur][it].first == par)continue;
ll length = dfs(adj[cur][it].first, cur, adj[cur][it].second);
if(length >= first_max) {
second_max = first_max;
first_max = length;
}
else if(length >= second_max) {
second_max = length;
}
}
max_length = max(max_length, first_max + second_max);
return (ll)last_weight + first_max;
}
int to[LIM + 1], L[LIM + 1];
bitset<LIM + 1> need;
void solve() {
int N; cin >> N;
for(int i = 1; i <= N; ++i) {
cin >> to[i] >> L[i];
add_edge(i, to[i], L[i]);
if(to[i] < i && to[to[i]] == i) {
need[to[i]] = 0;
length_two_cycle[i] = 1;
length_two_cycle[to[i]] = 1;
}
else {
need[i] = 1;
}
}
for(int i = 1; i <= N; ++i) {
add_edge(to[i], i, L[i]);
}
ll answer = 0;
for(int i = 1; i <= N; ++i) {
if(!vis[i]){
vector<int>().swap(cycle);
vector<int>().swap(st);
vector<int>().swap(cycle_weight);
vector<int>().swap(weight);
dfs_cycle(i);
max_length = 0;
ll total_length = 0, current_length = 0, regular_max = -1e18, reverse_max = -1e18;
// for(int j = 0; j < cycle.size(); ++j) {
// cout << cycle[j] << " " << cycle_weight[j] << "\n";
// }
for(int elem : cycle_weight) {
total_length += (ll)elem;
}
for(int j = 0; j < cycle.size(); ++j) {
ll depth = dfs(cycle[j]);
if(j > 0) {
max_length = max(max_length, regular_max + depth + current_length);
max_length = max(max_length, reverse_max + depth - current_length + total_length);
}
regular_max = max(regular_max, depth - current_length);
reverse_max = max(reverse_max, depth + current_length);
current_length += cycle_weight[j];
//cout << "| " << cycle[j] << " " << current_length << " " << regular_max << " " << reverse_max << "\n";
}
//cout << max_length << "\n";
answer += max_length;
}
}
cout << answer;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int tc = 1; //cin >> tc;
while(tc--) {
solve();
}
return 0;
}
