#include<algorithm>
#include<iostream>
#include<map>
#include<queue>
#include<vector>
using namespace std;
typedef long long lint;
typedef vector<int>vi;
typedef pair<int,int>pii;
typedef pair<lint,int>pli;
#define rep(i,n)for(int i=0;i<int(n);++i)

#define I (1LL<<53)
#define N 210000

map<pii,int>bank;
vector<pii>sky[N];
vector<vector<pii> >g;

int regist(int a,int b){
  if(bank.count(pii(a,b))){
    return bank[pii(a,b)];
  }
  int s=bank.size();
  bank[pii(a,b)]=s;
  sky[a].push_back(pii(b,s));
  return s;
}


int main(){
  int n,m,k,s,t;
  cin>>n>>m>>k>>s>>t;
  vi ds(m),es(m);
  rep(i,m){
    int a,b,c;
    cin>>a>>b>>c;
    a--;
    int d=regist(a,b);
    int e=regist(a+1,c);
    ds[i]=d;
    es[i]=e;
  }
  int si=regist(0,s);
  int ti=regist(n-1,t);
  int gs=bank.size();
  g=vector<vector<pii> >(gs);
  rep(i,m)g[ds[i]].push_back(pii(es[i],0));
  rep(i,n){
    sort(sky[i].begin(),sky[i].end());
    if(sky[i].size()==0)continue;
    rep(j,sky[i].size()-1){
      pii vvh=sky[i][j];
      int v=vvh.second;
      int vh=vvh.first;
      pii wwh=sky[i][j+1];
      int w=wwh.second;
      int wh=wwh.first;
      g[v].push_back(pii(w,wh-vh));
      g[w].push_back(pii(v,wh-vh));
    }
  }
  vector<lint>dis(gs,I);
  priority_queue<pli,vector<pli>,greater<pli> >q;
  q.push(pli(0,si));
  while(q.size()>0){
    pli dw=q.top();q.pop();
    lint d=dw.first;
    int v=dw.second;
    if(dis[v]<=d)continue;
    dis[v]=d;
    for(pii e:g[v]){
      int w=e.first;
      long nd=d+e.second;
      if(dis[w]<=nd)continue;
      dis[w]=nd+1;
      q.push(pli(nd,w));
    }
  }
  cout<<(dis[ti]==I?-1:dis[ti])<<endl;
}