#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
vector<int> par,sz,swappable,deg,has;
int total_groups;
void init(int n){
par.resize(n); sz.resize(n); swappable.resize(n); deg.resize(n);has.resize(n);
for(int i=0;i<n;i++){
par[i]=i;
sz[i]=1;
swappable[i]=0;
deg[i]=0;
has[i]=0;
}
}
int find(int x){
if(par[x]==x) return x;
else return par[x]=find(par[x]);
}
void sw(int x,int y){
swappable[x]=(swappable[x]&swappable[y]);
swappable[y]=(swappable[x]&swappable[y]);
has[x]|=has[y];
if(has[x]){
swappable[y]=1;
swappable[x]=1;
}
}
void unite(int x, int y) {
x = find(x);
y = find(y);
if (x == y) return;
if (sz[x] < sz[y]) swap(x, y);
sw(x,y);
par[y] = x;
sz[x] += sz[y];
total_groups--;
}
bool same(int x,int y){
x = find(x);
y = find(y);
if(x==y) return true;
else return false;
}
//remember to init(n+5) and total_groups=n
struct edge{
int u,v,d;
};
bool operator <(edge a,edge b){
return a.d<b.d;
}
#include "swap.h"
int n,m,ok=1,mx=-1;
int sub1=1,sub2=1,sub4=1,sub5=1;
vector<int> tw;
vector<vector<pair<int,int>>> adj;
vector<edge> ed;
void init(int N, int M, vector<int> U, vector<int> V, vector<int> W) {
n=N,m=M;tw.resize(n+2);
adj.resize(n + 2);
for (int i = 0; i < m; i++) {
adj[U[i]].push_back(make_pair(V[i],W[i]));
adj[V[i]].push_back(make_pair(U[i], W[i]));
mx = max(mx, W[i]);
}
for (int i = 0; i < n; i++) {
sub1&=(adj[i].size() <= 2);
ok&=(adj[i].size()==2);
}
for(int i=0;i<m;i++){
if(U[i]!=0) sub2=0;
tw[V[i]]=W[i];
}
for(int i=0;i<m;i++){
ed.pb({U[i],V[i],W[i]});
}
sort(ed.begin(),ed.end());
}
int getMinimumFuelCapacity(int X, int Y) {
if(sub1){
if(ok) return mx;
else return -1;
}
if(sub2){
if(m<=2) return -1;
if(X>Y) swap(X,Y);
if(X!=0){//if both at side
int ret=max(tw[Y],tw[X]);
int cnt=0;
while(ed[cnt].v==X || ed[cnt].v==Y) cnt++;
ret=max(ret,ed[cnt].d);
return ret;
}
else{
int ret=tw[Y],tmp,cnt=0;
while(ed[cnt].v==Y) cnt++;
ret=max(ret,ed[cnt].d);
tmp=ed[cnt].v;
cnt++;
while(ed[cnt].v==Y || ed[cnt].v==tmp) cnt++;
ret=max(ret,ed[cnt].d);
return ret;
}
}
init(n+2);
int i=0;
while(i<=m-1 && (!same(X,Y) || !swappable[find(X)])){
deg[ed[i].u]++; deg[ed[i].v]++;
if(same(ed[i].u,ed[i].v)) has[find(ed[i].u)]=1;
if(deg[ed[i].u]>=3) has[find(ed[i].u)]=1;
if(deg[ed[i].v]>=3) has[find(ed[i].v)]=1;
unite(ed[i].u,ed[i].v);
if(same(X,Y) && has[find(X)]==1) return ed[i].d;
i++;
}
return -1;
}
/*int main(){
int tt; cin>>tt;
while(tt--){
int n,m; cin>>n>>m;
vector<int>u(m),v(m),w(m);
for(int i=0;i<m;i++) cin>>u[i]>>v[i]>>w[i];
init(n,m,u,v,w);
int q; cin>>q;
for(int i=0;i<q;i++){
int x,y; cin>>x>>y;
cout<<getMinimumFuelCapacity(x,y)<<'\n';
}
}
}*/
