#include <bits/stdc++.h>

int ri() {
	int n;
	scanf("%d", &n);
	return n;
}

template<typename T> using pqueue_inv = std::priority_queue<T, std::vector<T>, std::greater<T> >;

const double DINF = 1000000000;

int main() {
	int n = ri();
	int m = ri();
	int x = ri() - 1, y = ri() - 1;
	std::pair<int, int> pts[n];
	for (auto &i : pts) i.first = ri(), i.second = ri();
	auto calc_dist = [&] (int i, int j) {
		return std::hypot(pts[i].first - pts[j].first, pts[i].second - pts[j].second);
	};
	
	std::vector<std::pair<int, double> > hen[n];
	for (int i = 0; i < m; i++) {
		int x = ri() - 1;
		int y = ri() - 1;
		hen[x].push_back({y, calc_dist(x, y)});
		hen[y].push_back({x, calc_dist(x, y)});
	}
	
	auto dijkstra = [&] (int s, int t) {
		std::vector<double> dist(n, DINF);
		pqueue_inv<std::pair<double, int> > que;
		que.push({dist[s] = 0, s});
		while (que.size()) {
			auto j = que.top();
			que.pop();
			if (j.second == t) return dist[t];
			if (j.first != dist[j.second]) continue;
			for (auto k : hen[j.second]) {
				if (dist[k.first] > j.first + k.second) que.push({dist[k.first] = j.first + k.second, k.first});
			}
		}
		return dist[t];
	};
	printf("%.11f\n", dijkstra(x, y));
	return 0;
}