#include <cstdio>#include <cstring>#include <cstdlib>#include <iostream>#include <algorithm>#include <queue>#include <stack>#define N 1000100using namespace std;int n, power[N];int p[N] = {0}, next[N*2], v[N*2], bnum = -1;long long f1[N][2] = {0}, f2[N][2] = {0};void addbian(int x, int y){    bnum++; next[bnum] = p[x]; p[x] = bnum; v[bnum] = y;    bnum++; next[bnum] = p[y]; p[y] = bnum; v[bnum] = x;}int root, ban;int cannot;bool vis[N] = {0};void dfs(int now, int fa){    int k = p[now];    while (k != -1)    {        if ((k^1) != fa && v[k] != ban)        {            if (vis[v[k]])            {                root = v[k];                ban = now;                cannot = k^1;            }            else            {                vis[v[k]] = 1;                dfs(v[k], k);            }        }        k = next[k];    }}void makeans_root(int now, int fa){    int k = p[now];    if (now == ban)    {        while (k != -1)        {            if ((k^1) != fa && v[k] != root)            {                makeans_root(v[k], k);                f1[now][0] += max(f1[v[k]][0], f1[v[k]][1]);                f1[now][1] += f1[v[k]][0];            }            k = next[k];        }        return;    }    f1[now][1] = power[now];    while (k != -1)    {        if ((k^1) != fa && k != cannot)        {            makeans_root(v[k], k);            f1[now][0] += max(f1[v[k]][0], f1[v[k]][1]);            f1[now][1] += f1[v[k]][0];        }        k = next[k];    }    return;}void makeans_ban(int now, int fa){    int k = p[now];    if (now == ban)    {        f2[now][1] = power[now];        while (k != -1)        {            if ((k^1) != fa && v[k] != root)            {                makeans_ban(v[k], k);                f2[now][0] += max(f2[v[k]][0], f2[v[k]][1]);                f2[now][1] += f2[v[k]][0];            }            k = next[k];        }        return;    }    f2[now][1] = power[now];    while (k != -1)    {        if ((k^1) != fa && k != cannot)        {            makeans_ban(v[k], k);            f2[now][0] += max(f2[v[k]][0], f2[v[k]][1]);            f2[now][1] += f2[v[k]][0];        }        k = next[k];    }    return;}int main(){    scanf("%d", &n);    for (int i = 1; i <= n; ++i) p[i] = -1;    for (int i = 1; i <= n; ++i)    {        int x; scanf("%d%d", &power[i], &x);        addbian(x, i);    }    long long ans = 0;    for (int i = 1; i <= n; ++i)        if (!vis[i])        {            root = -1; ban = -1;            vis[i] = 1; dfs(i, -1);            makeans_root(root, -1);            makeans_ban(root, -1);            long long zans = 0;            zans = max(f1[root][1], zans);            zans = max(zans, f1[root][0]);            zans = max(f2[root][0], zans);            ans += zans;        }    printf("%lld\n", ans);}