#include <bits/stdc++.h>
using namespace std;
bool vis[1000001];
vector<pair<int, int> > edge[1000001];
long long dp1[1000001], dp2[1000001];
vector<int> vec;
void dfs(int x){
vec.push_back(x);
vis[x] = 1;
dp1[x] = dp2[x] = 0;
long long mx1 = 0, mx2 = 0;
for(auto i: edge[x]){
if(vis[i.second]) continue;
dfs(i.second);
dp1[x] = max(dp1[x], dp1[i.second]);
long long t = dp2[i.second]+i.first;
dp2[x] = max(dp2[x], t);
if(mx1 <= t) mx2 = mx1, mx1 = t;
else if(mx2 < t) mx2 = t;
}
dp1[x] = max(dp1[x], mx1+mx2);
}
long long getD(int x){
dfs(x);
return dp1[x];
}
int main(){
ios_base::sync_with_stdio(0), cin.tie(0);
int N; cin>>N;
for(int i=1; i<=N; ++i){
int a,b; cin>>a>>b;
edge[i].push_back({b, a});
edge[a].push_back({b, i});
}
long long ans = 0;
for(int i=1; i<=N; ++i){
if(vis[i]) continue;
long long t = getD(i);
for(auto j: vec) reverse(edge[j].begin(), edge[j].end()), vis[j] = 0;
vec.clear();
t = max(t, getD(i));
vec.clear();
ans += t;
}
cout<<ans;
return 0;
}
