mod = 1000000007
eps = 10**-9


def main():
    import sys
    import heapq
    from math import hypot
    input = sys.stdin.buffer.readline

    def dijkstra(adj, start):
        # adj: [[to, cost] * vertices], 0th index must be empty
        inf = float("inf")
        dist = [inf] * len(adj)
        dist[start] = 0
        q = []
        heapq.heappush(q, (0, start))
        while q:
            min_dist, v_from = heapq.heappop(q)
            if min_dist > dist[v_from]:
                continue
            v_tos = adj[v_from]
            for v_to, cost in v_tos:
                if min_dist + cost < dist[v_to]:
                    dist[v_to] = min_dist + cost
                    heapq.heappush(q, (dist[v_to], v_to))
        return dist

    N, M = map(int, input().split())
    s, t = map(int, input().split())
    X = []
    Y = []
    for _ in range(N):
        p, q = map(int, input().split())
        X.append(p)
        Y.append(q)
    adj = [[] for _ in range(N+1)]
    for _ in range(M):
        i, j = map(int, input().split())
        d = hypot(X[i-1] - X[j-1], Y[i-1] - Y[j-1])
        adj[i].append((j, d))
        adj[j].append((i, d))

    dist = dijkstra(adj, s)
    print(dist[t])


if __name__ == '__main__':
    main()