#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
const int MAX_N = 1000001;
#define pii pair<int, int>
#define f first
#define s second
#define ll long long
int t[MAX_N], l[MAX_N], vis[MAX_N], b;
ll m, ans = 0;
vector<int> edges[MAX_N];
void dfs2(int x, int p, ll d, vector<int> &cur) {
cur.push_back(x);
if (d > m) {
m = d;
b = x;
}
for (int i : edges[x]) {
if (vis[i] && i != p) dfs2(i, x, d+l[i], cur);
}
if (vis[t[x]] && t[x] != p) dfs2(t[x], x, d+l[x], cur);
}
void dfs3(int x, int p, ll d) {
m = max(m, d);
for (int i : edges[x]) {
if ((vis[x] || vis[i]) && i != p) dfs3(i, x, d+l[i]);
}
if ((vis[x] || vis[t[x]]) && t[x] != p) dfs3(t[x], x, d+l[x]);
}
void solve(int v) {
ll best = 0, len = l[v], psa = 0, x = -1e9, y = -1e9;
for (int i=t[v]; i!=v; i=t[i]) len += l[i];
int i = v;
do {
vector<int> cur;
m = -1;
dfs2(i, i, 0, cur);
best = max(best, max(psa+m+x, len+m-psa+y));
x = max(x, m-psa);
y = max(y, m+psa);
psa += l[i];
m = -1;
dfs3(b, b, 0);
best = max(best, m);
i = t[i];
} while (i != v);
ans += best;
}
void dfs(int v, int c) {
vis[v] = c;
if (vis[t[v]] == c) {
vis[v] = 0;
for (int i=t[v]; i!=v; i=t[i]) vis[i] = 0;
solve(v);
}
if (vis[t[v]] == -1) dfs(t[v], c);
}
int main() {
int n;
scanf("%d", &n);
for (int i=1; i<=n; i++) {
scanf("%d%d", &t[i], &l[i]);
vis[i] = -1;
edges[t[i]].push_back(i);
}
for (int i=1; i<=n; i++) {
if (vis[i] == -1) dfs(i, i);
}
printf("%lld\n", ans);
}
