import sys
from math import sqrt
sys.setrecursionlimit(200010)
input = sys.stdin.readline

def main():
    N, M = map(int,input().split())
    X, Y = map(int,input().split())
    X -= 1
    Y -= 1
    D = []
    for _ in range(N):
        D.append(list(map(int,input().split())))
    K = [[] for _ in range(N)]
    for _ in range(M):
        P, Q = map(int,input().split())
        P -= 1
        Q -= 1
        K[P].append([Q,sqrt((D[P][0]-D[Q][0])**2+(D[P][1]-D[Q][1])**2)])
        K[Q].append([P,sqrt((D[P][0]-D[Q][0])**2+(D[P][1]-D[Q][1])**2)])
    V = [float("inf")]*N
    def dfs(ima):
        for tsugi in K[ima]:
            if V[tsugi[0]] > V[ima] + tsugi[1]:
                V[tsugi[0]] = V[ima] + tsugi[1]
                dfs(tsugi[0])
    V[X] = 0
    dfs(X)
    print(V[Y])
if __name__ == '__main__':
    main()