#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
using namespace std;

const long long INF = LLONG_MAX / 4;

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

    vector<vector<pair<int, int> > > edges(n+1);
    edges[0].push_back(make_pair(-1, s));
    edges[n].push_back(make_pair(t, -1));
    for(int i=0; i<m; ++i){
        int a, b, c;
        cin >> a >> b >> c;
        edges[a].push_back(make_pair(b, c));
    }

    vector<long long> dp(1, 0);
    for(int i=0; i<n; ++i){
        vector<tuple<int, int, bool> > v;
        for(unsigned j=0; j<edges[i].size(); ++j)
            v.push_back(make_tuple(edges[i][j].second, j, true));
        for(unsigned j=0; j<edges[i+1].size(); ++j)
            v.push_back(make_tuple(edges[i+1][j].first, j, false));

        vector<long long> nextDp(edges[i+1].size(), INF);
        long long cost = INF;
        sort(v.begin(), v.end());
        for(const auto& t : v){
            int pos, k;
            bool isInput;
            tie(pos, k, isInput) = t;
            if(isInput)
                cost = min(cost, dp[k] - pos);
            else
                nextDp[k] = min(nextDp[k], cost + pos);
        }
        
        cost = INF * 2;
        reverse(v.begin(), v.end());
        for(const auto& t : v){
            int pos, k;
            bool isInput;
            tie(pos, k, isInput) = t;
            if(isInput)
                cost = min(cost, dp[k] + pos);
            else
                nextDp[k] = min(nextDp[k], cost - pos);
        }

        dp.swap(nextDp);
    }

    if(dp[0] < INF)
        cout << dp[0] << endl;
    else
        cout << -1 << endl;

    return 0;
}