C++ :

#include <cstdio>
#include <cstring>
#include <climits>
#include <algorithm>
#include <cctype>
#include <cmath>
using namespace std;

int N=0,M=0,r1=0,r2=0;
class node{
	public:
		int s,t,v;
		bool operator < (const node& b) const {
			return v>b.v;
		}
}E[100010];

int F[100000]={0};
inline int find(int x){
	if(F[x]!=x) F[x]=find(F[x]);
	return F[x];
}

inline void Union(int x,int y){
	r1=find(x); r2=find(y);
	if(r1!=r2) F[r1]=r2;
}

int main(){
	//freopen("prison.in","r",stdin);
	//freopen("prison.out","w",stdout);
	scanf("%d%d",&N,&M);
	for(int i=1;i<=2*N+2;++i) F[i]=i;
	for(int i=1;i<=M;++i){
		scanf("%d%d%d",&E[i].s,&E[i].t,&E[i].v);
	}
	sort(E+1,E+M+1);
	for(int i=1;i<=M;++i){
		Union(E[i].s,E[i].t+N);	Union(E[i].t,E[i].s+N);
		if(find(E[i].s)==find(E[i].s+N) || find(E[i].t)==find(E[i].t+N) ){
			printf("%d\n",E[i].v);
  			fclose(stdin);
			fclose(stdout);
			return 0;
		}
	}
	printf("0\n");
	fclose(stdin);
	fclose(stdout);
	return 0;
}
/*4 6
1 4 2533
2 3 3511
1 2 28351
1 3 6617
2 4 1805
3 4 12883*/

Pascal :

type
  bian=record
    x,y,d:longint;
  end;
//==============================================================================
var
  f:Array[0..20000] of longint;
  h:array[0..20000] of longint;
  map:array[0..100000] of bian;
  n,m:longint;
//==============================================================================
procedure qsort(l,r:longint);
var
  i,j,mid:longint;
  t:bian;
begin
  i:=l;
  j:=r;
  mid:=map[(l+r) div 2].d;
  repeat
    while map[i].d>mid do inc(i);
    while map[j].d<mid do dec(j);
    if i<=j then
       begin
         t:=map[i];
         map[i]:=map[j];
         map[j]:=t;
         inc(i);
         dec(j);
       end;
  until i>j;
  if i<r then qsort(i,r);
  if l<j then qsort(l,j);
end;
//==============================================================================
procedure init;
var
  i:longint;
begin
  readln(n,m);
  fillchar(h,sizeof(h),0);
  for i:=1 to m do
    readln(map[i].x,map[i].y,map[i].d);

  for i:=1 to n do
    f[i]:=i;

  qsort(1,m);

//  for i:=1 to m do
//    writeln(map[i].d);
end;
//==============================================================================
function get(t:longint):longint;
begin
  if f[t]=t then exit(t);
  f[t]:=get(f[t]);
  exit(f[t]);
end;
//==============================================================================
procedure union(t1,t2:longint);
var
  xx,yy:longint;
begin
  xx:=get(t1);
  yy:=get(t2);
  if xx<>yy then f[xx]:=yy;
end;
//==============================================================================
procedure main;
var
  tx,ty,i,j:longint;
begin
  for i:=1 to m do
    begin
      tx:=get(map[i].x);
      ty:=get(map[i].y);

      if tx=ty then{如果同为一个监狱（并查集）}
         begin
           writeln(map[i].d);
           close(input);
           close(output);
           halt;
         end;

      if (h[map[i].x]=0) and (h[map[i].y]=0) then{如果都没有敌人就互为敌人}
         begin
           h[map[i].x]:=map[i].y;
           h[map[i].y]:=map[i].x;
           continue;
         end;

      if h[map[i].x]=0 then{如果x没敌人，就把y当x的敌人}
         begin
           h[map[i].x]:=map[i].y;
         end;

      if h[map[i].y]=0 then{如果y没敌人，就把x当y的敌人}
         begin
           h[map[i].y]:=map[i].x;
         end;
      union(h[map[i].x],map[i].y);{合并两个并查集}
      union(h[map[i].y],map[i].x);
    end;


  writeln(0);

end;
//==============================================================================
begin
 // assign(input,'prison.in'); reset(input);
  //assign(output,'prison.out'); rewrite(output);

  init;
  main;

  //close(input); close(output);
end.