from scipy.sparse.csgraph import dijkstra
from scipy.sparse import csr_matrix
import sys

input = sys.stdin.readline

int1 = lambda x: int(x) - 1


def main():
    N, M = map(int, input().split())
    X, Y = map(int1, input().split())

    P = [tuple(map(int, input().split())) for _ in range(N)]
    length, frm, to = [.0] * M, [0] * M, [0] * M
    for i in range(M):
        p, q = map(int1, input().split())
        length[i] = ((P[p][0] - P[q][0]) ** 2 + (P[p][1] - P[q][1]) ** 2) ** .5
        frm[i] = p
        to[i] = q

    matr = csr_matrix((length, (frm, to)), shape=(N, N))
    print(dijkstra(matr, indices=X, directed=False)[Y])


if __name__ == '__main__':
    main()