#include <ctime>
#include <iostream>
#include <iomanip>
#include <vector>
#include <utility>
#include <queue>
#include <algorithm>

using namespace std;

// TEMPLATE {{{
#ifndef LOCAL
#define OJ 1
#else
#define OJ 0
#endif

#define endl '\n'
#define TIMESTAMP merr << "Execution time: " << fixed << setprecision(3) << (double)clock()/CLOCKS_PER_SEC << " s.\n"
class C_ {}; template <typename T> C_& operator <<(C_& __m, const T& __s) { if (!OJ) cerr << "\E[91m" << __s << "\E[0m"; return __m; }
C_ merr;

struct __s { __s() { if (OJ) { ios_base::Init i; cin.sync_with_stdio(0); cin.tie(0); } } ~__s(){ TIMESTAMP; } } __S;
/// END OF TEMPLATE }}}

vector<pair<int,long long> > G[111111];
long long D[111111];
int n,m,source,dest;

void input() {
  cin >> n >> m >> source >> dest;
  for (int i = 0; i < m; i++) {
    int u,v,w;
    cin >> u >> v >> w;
    G[u].push_back(make_pair(v,w));
    G[v].push_back(make_pair(u,w));
  }
}

void gen()
{
  int M = 30;
  int W = (int)8e8;
  source = 90;
  dest = 1;
  for (int i = 0; i < M; i++)
    G[i].push_back(make_pair(i + 1, 0));
  G[0].push_back(make_pair(M, W));
  n = M;

  for (int i = 0; i < M; i++)
  {
    G[n].push_back(make_pair(n + 2, W >> i));
    G[n].push_back(make_pair(n + 1, 0));
    G[n + 1].push_back(make_pair(n + 2, 0));
    n += 2;
  }
  n++;
  for (int i = 0; i < n; i++)
    random_shuffle(G[i].begin(), G[i].end());
}

void gen1() {
  n = 60;
  m = 0;
  source = n-1;
  dest = 1;
  for (int i = 0; i < n; i++) {
    for (int j = i+1; j < n; j++) {
      long long w = j-i;
      for (int k = i+1; k <= j; k++) {
        w += (1LL<<k);
      }
      G[i].push_back(make_pair(j,w));
      G[j].push_back(make_pair(i,w));
      m++;
    }
  }
}

int main(void) {
  queue<int> Q;
  long long ans;
  long long idx = 0;
  for (int i = 0; i < 111111; i++) { D[i] = 1000000000000000000LL; }
  //input();
  gen();
  //merr << "m = " << m << '\n';
  D[source] = 0;
  Q.push(source);
  while (Q.size()) {
    idx++;
    int v = Q.front();
    Q.pop();
    for (int i = 0; i < (int)G[v].size(); i++) {
      int vv = G[v][i].first;
      long long ww = G[v][i].second;
      if (D[vv] > D[v]+ww) {
        D[vv] = D[v]+ww;
        Q.push(vv);
      }
    }
  }
  ans = D[dest];
  if (ans >= 1000000000000000000LL) ans = -1;
  cout << ans << endl;
  merr << "idx = " << idx << '\n';
  return 0;
}