#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <queue>

using namespace std;

int main() {
  int n, m, k, s, t;
  cin >> n >> m >> k >> s >> t;

  vector<int> a(m), b(m), c(m);
  vector<vector<int>> g(n), gg(n);
  g[0].push_back(s);
  g[n - 1].push_back(t);
  for (int i = 0; i < m; i++) {
    scanf("%d %d %d", &a[i], &b[i], &c[i]);
    g[a[i] - 1].push_back(b[i]);
    g[a[i]    ].push_back(c[i]);
    gg[a[i] - 1].push_back(i);
  }
  vector<vector<long long>> dp(n);
  for (int i = 0; i < n; i++) {
    sort(g[i].begin(), g[i].end());
    g[i].erase(unique(g[i].begin(), g[i].end()), g[i].end());
    dp[i].resize(g[i].size(), 1e18);
  }
  auto index = [&](vector<int> &a, int v) { return lower_bound(a.begin(), a.end(), v) - a.begin(); };
  int S = index(g[0], s);
  int T = index(g[n - 1], t);
  dp[0][S] = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j + 1 < g[i].size(); j++) {
      dp[i][j + 1] = min(dp[i][j + 1], dp[i][j] + g[i][j + 1] - g[i][j]);
    }
    for (int j = (int)g[i].size() - 2; j >= 0; j--) {
      dp[i][j] = min(dp[i][j], dp[i][j + 1] + g[i][j + 1] - g[i][j]);
    }
    for (int j : gg[i]) {
      int u = index(g[i], b[j]);
      int v = index(g[i + 1], c[j]);
      dp[i + 1][v] = min(dp[i + 1][v], dp[i][u]);
    }
  }
  if (dp[n - 1][T] >= 1e17) {
    cout << -1 << endl;
  } else {
    cout << dp[n - 1][T] << endl;
  }
}