4 6
1 4 2534
2 3 3512
1 2 28351
1 3 6618
2 4 1805
3 4 12884

3512

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
#define maxn 20000*3
#define maxm 100000*3
int fa[maxn],n,m;
struct node{int from,to,v;}e[maxm];
int cmp(node a,node b){return a.v>b.v;}
int find(int x){if(fa[x]==x)return fa[x];else return fa[x]=find(fa[x]);
}
int main(){scanf("%d%d",&n,&m);int x,y,z;for(int i=1;i<=m;i++){scanf("%d%d%d",&x,&y,&z);e[i].from=x;e[i].to=y;e[i].v=z;}sort(e+1,e+m+1,cmp);for(int i=1;i<=n*2;i++)fa[i]=i;for(int i=1;i<=m;i++){int f1=find(e[i].from);int f2=find(e[i].to);if(f1==f2){printf("%d",e[i].v);return 0;}fa[f1]=find(e[i].to+n);fa[f2]=find(e[i].from+n);}printf("0");return 0;
}

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define maxm 100010
#define maxn 20010
int n,head[maxm*2],m,num,l,r,vis[maxn];
struct node{int to,pre,v;
}e[maxm*2];
bool flag;
void Insert(int from,int to,int v){e[++num].to=to;e[num].v=v;e[num].pre=head[from];head[from]=num;
}
void dfs(int fa,int now,int limit){if(flag)return;for(int i=head[now];i;i=e[i].pre){int to=e[i].to;if(e[i].v>limit&&to!=fa){if(!vis[to]){vis[to]=-vis[now];dfs(now,to,limit);}else if(vis[to]==vis[now]){flag=1;return;}}}
}
bool check(int x){memset(vis,0,sizeof(vis));flag=false;for(int i=1;i<=n;i++){if(!vis[i]){vis[i]=1;dfs(i,i,x);}}if(flag)return false;return true;
}
int main(){scanf("%d%d",&n,&m);int x,y,z;for(int i=1;i<=m;i++){scanf("%d%d%d",&x,&y,&z);r=max(r,z);Insert(x,y,z);Insert(y,x,z);}while(l<=r){int mid=(l+r)>>1;if(check(mid))r=mid-1;else l=mid+1;}printf("%d",l);
}