C++ :

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

struct AngryInt
{
  int a,b;
  long long c;
}ang[100001];
int N,M,h[40001];
bool flag;
int Find(int x)
{
  if(h[x]==x)
    return x;
  return h[x]=Find(h[x]);
}
bool comp(AngryInt x,AngryInt y)
{
  return x.c<y.c;
}
int main()
{
  cin>>N>>M;
  for(int i=1;i<=N*2;i++)
    h[i]=i;
  for(int i=1;i<=M;i++)
    scanf("%d%d%lld",&ang[i].a,&ang[i].b,&ang[i].c);
  sort(ang+1,ang+M+1,comp);
  for(int i=M;i>=1;i--)
  {
    int x=Find(ang[i].a),y=Find(ang[i].b);
    if(x==y)
    {
      printf("%lld",ang[i].c);
      flag=true;
      break;
    }
    else
    {
      h[x]=Find(ang[i].b+N);
      h[y]=Find(ang[i].a+N);
    }
  }
  if(!flag)
    printf("0");
  return 0;
}

Pascal :

program prison;
var
 a,b,c:array[1..100000]of longint;
 f,h:array[1..20000]of longint;
 m,n,i,j,t:longint;
procedure qs(l,r:longint);
var
 i,j,m:longint;
begin
 i:=l; j:=r; m:=c[(i+j) div 2];
 repeat
  while c[i]>m do inc(i);
  while c[j]<m do dec(j);
  if i<=j then
   begin
    t:=c[i]; c[i]:=c[j]; c[j]:=t;
    t:=a[i]; a[i]:=a[j]; a[j]:=t;
    t:=b[i]; b[i]:=b[j]; b[j]:=t;
    inc(i);
    dec(j);
   end;
 until i>j;
 if j>l then qs(l,j);
 if i<r then qs(i,r);
end;
procedure init;
begin
 readln(n,m);
 for i:= 1 to n do f[i]:=i;
 for i:= 1 to m do
   readln(a[i],b[i],c[i]);
 qs(1,m);
end;
function get(i:longint):longint;
begin
 if i=f[i] then exit(i);
 f[i]:=get(f[i]);
 exit(f[i]);
end;
procedure union(a,b:longint);
var
 x,y:longint;
begin
 x:=get(a);
 y:=get(b);
 if x<>y then f[x]:=y;
end;
procedure main;
var
 x,y,i,j:longint;
begin
 for i:= 1 to m do
  begin
   x:=get(a[i]);
   y:=get(b[i]);
   if x=y then
    begin
     writeln(c[i]);
     halt;
    end;
   if (h[a[i]]=0)and(h[b[i]]=0) then
    begin
     h[a[i]]:=b[i];
     h[b[i]]:=a[i];
     continue;
    end;
   if h[a[i]]=0 then h[a[i]]:=b[i];
   if h[b[i]]=0 then h[b[i]]:=a[i];
   union(b[i],h[a[i]]);
   union(a[i],h[b[i]]);
  end;
  writeln(0);
end;
begin
 init;
 main;
end.