#include <iostream>
#include <algorithm>
#include <utility>
#include <vector>
#include <numeric>
#include <cmath>
#include <queue>
#include <iomanip>

template <class T, class U>
inline bool chmin(T &lhs, const U &rhs) {
  if (lhs > rhs) {
    lhs = rhs;
    return true;
  }
  return false;
}

template <class T, class U>
inline bool chmax(T &lhs, const U &rhs) {
  if (lhs < rhs) {
    lhs = rhs;
    return true;
  }
  return false;
}

// [l, r) from l to r
struct range {
  struct itr {
    int i;
    constexpr itr(int i_): i(i_) { }
    constexpr void operator ++ () { ++i; }
    constexpr int operator * () const { return i; }
    constexpr bool operator != (itr x) const { return i != x.i; }
  };
  const itr l, r;
  constexpr range(int l_, int r_): l(l_), r(std::max(l_, r_)) { }
  constexpr itr begin() const { return l; }
  constexpr itr end() const { return r; }
};

// [l, r) from r to l
struct revrange {
  struct itr {
    int i;
    constexpr itr(int i_): i(i_) { }
    constexpr void operator ++ () { --i; }
    constexpr int operator * () const { return i; }
    constexpr bool operator != (itr x) const { return i != x.i; }
  };
  const itr l, r;
  constexpr revrange(int l_, int r_): l(l_ - 1), r(std::max(l_, r_) - 1) { }
  constexpr itr begin() const { return r; }
  constexpr itr end() const { return l; }
};

int main() {
  int N, M;
  std::cin >> N >> M;
  int S, G;
  std::cin >> S >> G;
  --S; --G;
  std::vector<double> X(N), Y(N);
  for (int i: range(0, N)) {
    std::cin >> X[i] >> Y[i];
  }
  std::vector<std::vector<std::pair<int, double>>> graph(N);
  for (int i: range(0, M)) {
    int x, y;
    std::cin >> x >> y;
    --x; --y;
    double d = std::hypot(X[x] - X[y], Y[x] - Y[y]);
    graph[x].emplace_back(y, d);
    graph[y].emplace_back(x, d);
  }
  std::vector<double> dist(N, 1e9);
  using state = std::pair<double, int>;
  std::priority_queue<state, std::vector<state>, std::greater<state>> que;
  dist[S] = 0;
  que.emplace(dist[S], S);
  while (!que.empty()) {
    auto [d, u] = que.top();
    que.pop();
    if (d > dist[u]) {
      continue;
    }
    for (auto e: graph[u]) {
      if (chmin(dist[e.first], dist[u] + e.second)) {
        que.emplace(dist[e.first], e.first);
      }
    }
  }
  std::cout << std::fixed << std::setprecision(20);
  std::cout << dist[G] << '\n';
  return 0;
}