#include <cstdio>
#include <vector>
#include <algorithm>
#define debug(...) //fprintf(stderr, __VA_ARGS__)
#define X first
#define Y second
#define PB push_back
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int N = 1e6 + 10;
int n, weg[N];
vector<pii> g[N];
int bio[N];
vector<pii> cyc;
int dfs(int u, int p) {
bio[u] = 1;
for(pii e : g[u]) {
int v = e.X, w = e.Y;
if(w != p) {
if(bio[v]) {
cyc.PB({e.X, weg[e.Y]});
return v;
} else {
int res = dfs(v, w);
if(res) {
cyc.PB({e.X, weg[e.Y]});
return res != u ? res : 0;
}
}
}
}
bio[u] = 0;
return 0;
}
void mark(int u) {
bio[u] = 2;
for(pii e : g[u]) {
if(bio[e.X] != 2) {
mark(e.X);
}
}
}
ll dep[N];
ll depth(int u, int p) {
for(pii e : g[u]) {
int v = e.X, w = e.Y;
if(w != p && !bio[v]) {
dep[u] = max(dep[u], (ll) weg[w] + depth(v, w));
}
}
return dep[u];
}
int main() {
scanf("%d", &n);
for(int i = 1; i <= n; ++i) {
int u, w;
scanf("%d%d", &u, weg + i);
g[i].PB({u, i});
g[u].PB({i, i});
}
ll ans = 0;
for(int i = 1; i <= n; ++i) {
if(bio[i]) { continue; }
cyc.clear();
dfs(i, 0);
for(pii e : cyc) {
depth(e.X, 0);
debug("%d(%d, %lld)\n", e.X, e.Y, dep[e.X]);
}
ll res = dep[cyc.front().X], xam = dep[cyc.front().X], prf = cyc.front().Y;
for(int i = 1; i < cyc.size(); ++i) {
res = max(dep[cyc[i].X] + xam + prf, res);
xam = max(dep[cyc[i].X] - prf, xam);
prf += cyc[i].Y;
}
xam = dep[cyc.front().X];
prf = 0;
for(int i = (int) cyc.size() - 1; i > 0; --i) {
prf += cyc[i].Y;
res = max(dep[cyc[i].X] + xam + prf, res);
xam = max(dep[cyc[i].X] - prf, xam);
}
ans += res;
mark(i);
debug("+ %lld\n", res);
}
printf("%lld\n", ans);
return 0;
}
