求助!27分实在查不出来哪里错了！

是check()函数出现的问题，似乎只有限定fm为(f[i])max的时候check才会成功。恳请dalao帮忙指点！

#include<cstdio>
#include<iostream>
#include<cstring>
#include<string>
#include<queue>
#include<algorithm>
#include<cstdlib>
#define max(a,b) (a>b?a:b)
#define min(a,b) (a<b?a:b)
#define maxn 10000+100
#define maxm 50000<<1
#define INF 0x3f3f3f3f
#define LL long long 
using namespace std;
LL n,m,f[maxn],b,ans,f1,fn,dis[maxn];
bool vis[maxn];
struct edge{
    int u,v,c,nxt;
}g[maxm];
struct node{
    int u;LL d;
    bool operator < (const node& a) const{
        return this->d<a.d;
    }
};
int pre[maxn],cnt;
inline void edgeadd(int u,int v,int c)
{
    g[++cnt].u=u;
    g[cnt].v=v;
    g[cnt].c=c;
    g[cnt].nxt=pre[u];
    pre[u]=cnt;
}
LL read()
{
    char c=getchar();int x=0;
    while(c<'0'||c>'9') c=getchar();
    while(c>='0'&&c<='9') {x=x*10+c-'0';c=getchar();}
    return x;
}
bool check(long long fm)
{
    memset(vis,0,sizeof(vis));
    memset(dis,0x3f,sizeof(dis));
    for(int i=1;i<=n;i++)
      if(f[i]>fm) vis[i]=1;
    dis[1]=0;
    priority_queue<node> q;
    q.push((node){1,dis[1]});
    while(!q.empty())
      {
         node x=q.top();q.pop();
         int u=x.u;
         if(vis[u]) continue;
         vis[u]=1;
         for(int i=pre[u];i;i=g[i].nxt)
           {
              int v=g[i].v,c=g[i].c;
              if(f[v]>fm) continue;
              if(dis[v]>dis[u]+c)
                {
                    dis[v]=dis[u]+c;
                    q.push((node){v,dis[v]});
                }
           }    
      }
    ans=dis[n];
    return (b>ans);
}
int lower(int l,int r,int key)
{
    while(l<=r)
      {
         int mid=(l+r)>>1;
         if(f[mid]>key) r=mid-1;
         if(f[mid]==key) return mid;
         if(f[mid]<key) l=mid+1;
      }
    return -1;
}
int main()
{
    freopen("in.txt","r",stdin);
    n=read();m=read();b=read();
    for(int i=1;i<=n;i++) 
      {f[i]=read();if(i==1) f1=f[i];if(i==n) fn=f[i];}
    f1=max(f1,fn);
    for(int i=1;i<=m;i++) 
      {
        int u=read(),v=read(),c=read();
        if(u==v) continue;
        edgeadd(u,v,c);edgeadd(v,u,c);
      }
    sort(f+1,f+1+n);
    int l=lower(1,n,f1),r=n;
    while(l<r)
      {
         int mid=(l+r)>>1;
         if(check(f[mid])) r=mid;
         else l=mid+1;
      }
    if(!check(f[r])) cout<<"AFK";
    else cout<<f[r];
    return 0;
}