#include<bits/stdc++.h>
using namespace std;
int main(){
  int n,m;
  cin>>n>>m;
  int h[n];
  for(int i=0;i<n;i++) cin>>h[i];
  vector<vector<int>> G(n);
  for(int i=0;i<m;i++){
    int u,v;
    cin>>u>>v;
    u--;v--;
    G[u].push_back(v);
    G[v].push_back(u);
  }
  int idx[n];
  iota(idx,idx+n,0);
  sort(idx,idx+n,[&](int i,int j){return h[i]<h[j];});
  vector<int> dp0(n,-1e9),dpn(n,-1e9);
  dp0[0]=0;
  dpn[n-1]=0;
  for(int i:idx){
    for(int j:G[i]) if(h[j]<h[i]){
      dp0[i]=max(dp0[i],dp0[j]+1);
      dpn[i]=max(dpn[i],dpn[j]+1);
    }
  }
  int k=-1,ind=-1;
  for(int i=0;i<n;i++){
    if(k<dp0[i]+dpn[i]+1){
      k=dp0[i]+dpn[i]+1;
      ind=i;
    }
  }
  cout<<k<<endl;
  if(k<0){
    return 0;
  }
  deque<int> DQ{ind};
  int i0=ind,in=ind;
  for(;dp0[i0]+dpn[in];){
    if(dp0[i0]){
      for(int to:G[i0]){
        if(dp0[to]+1==dp0[i0]){
          DQ.push_front(to);
          i0=to;
          break;
        }
      }
    }
    if(dpn[in]){
      for(int to:G[in]){
        if(dpn[to]+1==dpn[in]){
          DQ.push_back(to);
          in=to;
          break;
        }
      }
    }
  }
  int num=0;
  //for(int i:DQ) cout<<i+1<<" \n"[++num==DQ.size()];
}