n, m = gets.to_s.split.map{|t| t.to_i }
x, y = gets.to_s.split.map{|t| t.to_i - 1 }

xys = Array.new(n){ gets.to_s.split.map{|t| t.to_i } }

g = Array.new(n){ [] }
m.times do
  s, t = gets.to_s.split.map{|t| t.to_i - 1 }
  g[s] << t
  g[t] << s
end

inf = Float::INFINITY
d = [inf] * n
d[x] = 0
q = [x]

while ( v = q.shift )
  
  d_v = d[v] 
  g[v].each do |u|
    t = Math.hypot( xys[u][0] - xys[v][0], xys[u][1] - xys[v][1] )
    if d[u] > d_v + t
      d[u] = d_v + t
      q.push u
    end
  end
end

puts d[y]