#include <bits/stdc++.h>

using namespace std;

#define int long long
#define all(v) (v).begin(), (v).end()
#define resz(v, ...) (v).clear(), (v).resize(__VA_ARGS__)
#define reps(i, m, n) for(int i = (int)(m); i < (int)(n); i++)
#define rep(i, n) reps(i, 0, n)

template<class T1, class T2> void chmin(T1 &a, T2 b){if(a>b)a=b;}
template<class T1, class T2> void chmax(T1 &a, T2 b){if(a<b)a=b;}

using Pi = pair<int, int>;
using Ti = tuple<int, int, int>;
using vint = vector<int>;

const int inf = 1LL << 55;
const int mod = 1e9 + 7;

struct edge {
  int to, cost;
  edge(){}
  edge(int to, int cost):to(to), cost(cost){}
};
using Graph = vector<vector<edge>>;

signed main()
{
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(12);

  int N, M, K, S, T;
  cin >> N >> M >> K >> S >> T;
  --S, --T;
  map<int, int> mp;
  vector<vint> buil(N);
  int sz = 0;
  mp[S] = sz++;
  buil[0].push_back(S);
  mp[(N-1)*K+T] = sz++;
  buil[N-1].push_back(T);
  vint a(M), b(M), c(M);
  rep(i, M) {
    cin >> a[i] >> b[i] >> c[i];
    --a[i], --b[i], --c[i];
    if(!mp.count(a[i]*K+b[i])) {
      mp[a[i]*K+b[i]] = sz++;
      buil[a[i]].push_back(b[i]);
    }
    if(!mp.count((a[i]+1)*K+c[i])) {
      mp[(a[i]+1)*K+c[i]] = sz++;
      buil[a[i]+1].push_back(c[i]);
    }
  }
  Graph graph(sz);
  rep(i, N) {
    sort(all(buil[i]));
    rep(j, buil[i].size()-1) {
      int s = mp[i*K+buil[i][j]];
      int t = mp[i*K+buil[i][j+1]];
      int cost = buil[i][j+1]-buil[i][j];
      graph[s].emplace_back(t, cost);
      graph[t].emplace_back(s, cost);
    }
  }
  rep(i, M) {
    int s = mp[a[i]*K+b[i]];
    int t = mp[(a[i]+1)*K+c[i]];
    graph[s].emplace_back(t, 0);
  }
  vint mincost(sz, inf);
  priority_queue<Pi, vector<Pi>, greater<Pi>> que;
  mincost[mp[S]] = 0;
  que.emplace(0, mp[S]);
  while(!que.empty()) {
    Pi p = que.top(); que.pop();
    int v = p.second;
    if(mincost[v] < p.first) continue;
    if(v == mp[(N-1)*K+T]) {
      cout << mincost[v] << endl;
      return 0;
    }
    for(edge& e : graph[v]) {
      if(mincost[e.to] > mincost[v]+e.cost) {
	mincost[e.to] = mincost[v]+e.cost;
	que.emplace(mincost[e.to], e.to);
      }
    }
  }
  cout << -1 << endl;

  return 0;
}