FAST_IO = 1
if FAST_IO:
    import io, sys, atexit
    rr = iter(sys.stdin.read().splitlines()).next
    sys.stdout = _OUTPUT_BUFFER = io.BytesIO()
    @atexit.register
    def write():
        sys.__stdout__.write(_OUTPUT_BUFFER.getvalue())
else:
    rr = raw_input
rri = lambda: int(rr())
rrm = lambda: map(int, rr().split())

####
from collections import defaultdict as ddic
import heapq

def solve(N,M,X,Y,A,B):
    # A: powerpole locations
    # B: wires
    # Shortest path X to Y
    graph = ddic(list)
    for u, v in B:
        graph[u].append(v)
        graph[v].append(u)
    def dist_2d(u, v):
        x1, y1 = A[u - 1]
        x2, y2 = A[v - 1]
        return ((x1-x2)**2 + (y1-y2)**2)**0.5

    INF = float('inf')
    dist = ddic(lambda: INF)
    dist[X] = 0
    pq = [[0, X]]
    while pq:
        d, node = heapq.heappop(pq)
        if d > dist[node]: continue
        for nei in graph[node]:
            w = dist_2d(node, nei)
            d2 = d + w
            if d2 < dist[nei]:
                dist[nei] = d2
                heapq.heappush(pq, [d2, nei])
    return dist[Y]

    
    
N,M = rrm()
X,Y = rrm()
A = [rrm()  for _ in xrange(N)]
B = [rrm() for _ in xrange(M)]
print solve(N, M, X, Y, A, B)