# include "bits/stdc++.h"
using namespace std;
using LL = long long;
using ULL = unsigned long long;
const double PI = acos(-1);
template<class T>constexpr T INF() { return ::std::numeric_limits<T>::max(); }
template<class T>constexpr T HINF() { return INF<T>() / 2; }
template <typename T_char>T_char TL(T_char cX) { return tolower(cX); };
template <typename T_char>T_char TU(T_char cX) { return toupper(cX); };
const int vy[] = { -1, -1, -1, 0, 1, 1, 1, 0 }, vx[] = { -1, 0, 1, 1, 1, 0, -1, -1 };
const int dx[4] = { 0,1,0,-1 }, dy[4] = { 1,0,-1,0 };
int popcnt(unsigned long long n) { int cnt = 0; for (int i = 0; i < 64; i++)if ((n >> i) & 1)cnt++; return cnt; }
int d_sum(LL n) { int ret = 0; while (n > 0) { ret += n % 10; n /= 10; }return ret; }
int d_cnt(LL n) { int ret = 0; while (n > 0) { ret++; n /= 10; }return ret; }
LL gcd(LL a, LL b) { if (b == 0)return a; return gcd(b, a%b); };
LL lcm(LL a, LL b) { LL g = gcd(a, b); return a / g*b; };
# define ALL(qpqpq)           (qpqpq).begin(),(qpqpq).end()
# define UNIQUE(wpwpw)        sort(ALL((wpwpw)));(wpwpw).erase(unique(ALL((wpwpw))),(wpwpw).end())
# define LOWER(epepe)         transform(ALL((epepe)),(epepe).begin(),TL<char>)
# define UPPER(rprpr)         transform(ALL((rprpr)),(rprpr).begin(),TU<char>)
# define FOR(i,tptpt,ypypy)   for(LL i=(tptpt);i<(ypypy);i++)
# define REP(i,upupu)         FOR(i,0,upupu)
# define INIT                 std::ios::sync_with_stdio(false);std::cin.tie(0)

struct edge { int to; LL cost; };
int start;
LL d[404040]; //距離
vector<edge> vec[404040];

void dijkstra() {
	for (int i = 0; i < 404040; i++)d[i] = HINF<LL>();
	priority_queue<pair<LL, int>, std::vector<pair<LL, int>>, std::greater<pair<LL, int>>> pq;
	d[start] = 0;
	pq.push(make_pair(d[start], start));//cost,to
	while (!pq.empty()) {
		pair<LL, int> p = pq.top();
		pq.pop();
		int i = p.second;
		if (d[i] < p.first)continue;
		for (int k = 0; k < (int)vec[i].size(); k++) {
			edge e = vec[i][k];
			if (d[e.to] <= d[i] + e.cost)continue;
			d[e.to] = d[i] + e.cost;
			pq.push(make_pair(d[e.to], e.to));
		}
	}
}

int n, m, k, s, t;
int a[202020], b[202020], c[202020];
vector<int> v[202020];
map<int, int> mp[202020];
int main(){
    scanf("%d%d%d%d%d", &n, &m, &k, &s, &t);
    s--, t--;
    int idx = 0;
    mp[0][s] = idx++;
    v[0].emplace_back(s);
    mp[n - 1][t] = idx++;
    v[n - 1].emplace_back(t);
    REP(i, m){
        scanf("%d%d%d", &a[i], &b[i], &c[i]);
        
        a[i]--, b[i]--, c[i]--;
        
        v[a[i]].emplace_back(b[i]);
        v[a[i] + 1].emplace_back(c[i]);
        
        if(!mp[a[i]].count(b[i]))mp[a[i]][b[i]] = idx++;
        if(!mp[a[i] + 1].count(c[i]))mp[a[i] + 1][c[i]] = idx++;
        vec[mp[a[i]][b[i]]].emplace_back(edge{mp[a[i] + 1][c[i]], 0});
    }
    REP(i, n){
        sort(ALL(v[i]));
        REP(j, (int)v[i].size() - 1){
            if(v[i][j + 1] == v[i][j])continue;
            vec[mp[i][v[i][j + 1]]].emplace_back(edge{mp[i][v[i][j]], v[i][j + 1] - v[i][j]});
            vec[mp[i][v[i][j]]].emplace_back(edge{mp[i][v[i][j + 1]], v[i][j + 1] - v[i][j]});
        }
    }
    dijkstra();
    if(d[mp[n - 1][t]] == HINF<LL>()){
        cout << -1 << endl;
    }else{
        cout << d[1] << endl;
    }
}