#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
const int LIM = 1e6;
pair<int, int> cycle_next[LIM + 1];
bitset<LIM + 1> vis1, vis2;
int to[LIM + 1], L[LIM + 1], deg[LIM + 1];
ll max_depth[LIM + 1], diameter[LIM + 1];
void solve() {
int N; cin >> N;
for(int i = 1; i <= N; ++i) {
cin >> to[i] >> L[i];
deg[to[i]]++;
cycle_next[i] = make_pair(0, 0);
}
for(int i = 1; i <= N; ++i) {
if(!vis1[i]) {
int cur = i, weight = 0;
vector<pair<int, int>> st;
while(!vis1[cur]) {
vis1[cur] = 1;
st.push_back(make_pair(cur, weight));
weight = L[cur];
cur = to[cur];
}
if(!vis2[cur]) {
int last = cur, first = st.back().first;
while(st.back().first != last) {
pair<int, int> now = st.back(); st.pop_back();
cycle_next[now.first] = make_pair(st.back().first, now.second);
}
cycle_next[last] = make_pair(first, weight);
}
cur = i;
while(!vis2[cur]) {
vis2[cur] = 1;
cur = to[cur];
}
}
}
queue<int> q;
for(int i = 1; i <= N; ++i) {
if(deg[i] == 0) {
q.push(i);
}
}
while(!q.empty()) {
int cur = q.front(); q.pop();
int nx = to[cur]; ll length = L[cur] + max_depth[cur];
diameter[nx] = max(diameter[nx], diameter[cur]);
diameter[nx] = max(diameter[nx], max_depth[nx] + length);
max_depth[nx] = max(max_depth[nx], length);
deg[nx]--;
if(deg[nx] == 0) {
q.push(nx);
}
}
vis1 = 0;
ll answer = 0;
for(int i = 1; i <= N; ++i) {
if(cycle_next[i].first == 0 || vis1[i]) {
continue;
}
ll max_length = 0, total_length = 0, current_length = 0, regular_max = -1e18, reverse_max = -1e18;
int pos = i;
bool first = 1;
while(first || pos != i) {
if(first)first = 0;
vis1[pos] = 1;
max_length = max(max_length, diameter[pos]);
total_length += (ll)cycle_next[pos].second;
pos = cycle_next[pos].first;
}
//cout << "x " << total_length << "\n";
pos = i;
first = 1;
while(first || pos != i) {
if(!first) {
max_length = max(max_length, regular_max + max_depth[pos] + current_length);
max_length = max(max_length, reverse_max + max_depth[pos] - current_length + total_length);
}
else first = 0;
regular_max = max(regular_max, max_depth[pos] - current_length);
reverse_max = max(reverse_max, max_depth[pos] + current_length);
current_length += (ll)cycle_next[pos].second;
pos = cycle_next[pos].first;
//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;
}
