#pragma comment(linker, "/STACK:102400000,102400000")
#include<bits/stdc++.h>
#define il inline
#define reg register int
#define numb (ch^'0')
using namespace std;
typedef long long ll;
void rd(int &x){char ch;x=0;while(!isdigit(ch=getchar()));for(x=numb;isdigit(ch=getchar());x=x*10+numb);
}
namespace Miracle{
const int N=1e6+5;
int n;
struct node{int nxt,to;ll val;
}e[2*N];
int hd[N],cnt=1;
void add(int x,int y,int z){e[++cnt].nxt=hd[x];e[cnt].to=y;e[cnt].val=z;hd[x]=cnt;
}
bool vis[N];
bool on[N];//on the huan
bool in[N];
int to[N],v[N];
int sta[N],top;
int len;//huan chang
int mem[2*N],tot;
ll cos[2*N];
int q[2*N],l,r;
ll f[N];
ll ans;
ll sum;
ll zhi;
bool fl;
void dfs(int x,int in_edge){
//    cout<<" dfs "<<x<<" "<<fl<<" "<<top<<endl;vis[x]=1;sta[++top]=x;for(reg i=hd[x];i;i=e[i].nxt){int y=e[i].to;if(i==(in_edge^1)) continue;if(!vis[y]){dfs(y,i);}else if(!fl){fl=true;//    cout<<" find "<<top<<" : "<<sta[top]<<endl;int z;do{z=sta[top];on[z]=1;mem[++len]=z;top--;}while(z!=y);}}if(sta[top]==x) --top;//warning!!!
}
void dp(int x,int fa){//find farthestfor(reg i=hd[x];i;i=e[i].nxt){int y=e[i].to;if(y==fa) continue;if(on[y]) continue;dp(y,x);zhi=max(zhi,f[x]+e[i].val+f[y]);f[x]=max(f[x],e[i].val+f[y]);}
}
ll wrk(int st){sum=0;len=0;fl=false;top=0;dfs(st,0);for(reg i=1;i<=len;++i){zhi=0;dp(mem[i],0);sum=max(sum,zhi);mem[i+len]=mem[i];}l=1,r=0;cos[1]=0;for(reg i=2;i<=2*len;++i){cos[i]=(to[mem[i]]==mem[i-1])?v[mem[i]]:v[mem[i-1]];cos[i]+=cos[i-1];}for(reg i=1;i<=2*len;++i){while(l<=r&&i-q[l]>=len) ++l;if(i!=1) sum=max(sum,f[mem[q[l]]]-cos[q[l]]+cos[i]+f[mem[i]]);while(l<=r&&f[mem[q[r]]]-cos[q[r]]<=f[mem[i]]-cos[i]) --r;q[++r]=i;}return sum;
}
int main(){rd(n);int x;int z;for(reg i=1;i<=n;++i){rd(x);rd(z);to[i]=x;v[i]=z;add(i,x,z);add(x,i,z);}for(reg i=1;i<=n;++i){if(!vis[i]){ans+=wrk(i);}}printf("%lld",ans);return 0;
}}
int main(){Miracle::main();return 0;
}/*Author: *Miracle*Date: 2018/11/4 9:27:26
*/