/*
このコード、と～おれ!
Be accepted!
∧＿∧　
（｡･ω･｡)つ━☆・*。
⊂　　 ノ 　　　・゜+.
　しーＪ　　　°。+ *´¨)
 　　　　　　　　　.· ´¸.·*´¨) ¸.·*¨)
		  　　　　　　　　　　(¸.·´ (¸.·'* ☆
*/

#include <cstdio>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstring>
#include <vector>
#include <numeric>
#include <iostream>
#include <random>
#include <map>
#include <unordered_map>
#include <queue>
#include <regex>
#include <functional>
#include <complex>
#include <list>
#include <cassert>
#include <iomanip>
#include <set>
#include <stack>
#include <bitset>
/*多倍長整数/cpp_intで宣言
#include <boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
*/

//#pragma gcc target ("avx2")
//#pragma gcc optimization ("o3")
//#pragma gcc optimization ("unroll-loops")
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define rep1(i, n) for(int i = 1; i <= (n); ++i)
#define rep2(i, n) for(int i = 2; i < (n); ++i)
#define repr(i, n) for(int i = n; i >= 0; --i)
#define reprm(i, n) for(int i = n - 1; i >= 0; --i)
#define printynl(a) printf(a ? "yes\n" : "no\n")
#define printyn(a) printf(a ? "Yes\n" : "No\n")
#define printYN(a) printf(a ? "YES\n" : "NO\n")
#define printim(a) printf(a ? "possible\n" : "imposible\n")
#define printdb(a) printf("%.50lf\n", a) //少数出力
#define printLdb(a) printf("%.50Lf\n", a) //少数出力
#define printdbd(a) printf("%.16lf\n", a) //少数出力(桁少なめ)
#define prints(s) printf("%s\n", s.c_str()) //string出力
#define all(x) (x).begin(), (x).end()
#define allsum(a, b, c) ((a + b) * c / 2LL) //等差数列の和、初項,末項,項数
#define pb push_back
#define priq priority_queue
#define rpriq priq<int, vector<int>, greater<int>>
#define deg_to_rad(deg) (((deg)/360.0L)*2.0L*PI)
#define rad_to_deg(rad) (((rad)/2.0L/PI)*360.0L)
#define Please return
#define AC 0
#define manhattan_dist(a, b, c, d) (abs(a - c) + abs(b - d)) /*(a, b) から (c, d) のマンハッタン距離 */


using ll = long long;

constexpr int INF = 1073741823;
constexpr int MINF = -1073741823;
constexpr ll LINF = ll(4661686018427387903);
constexpr ll MOD = 1000000007;
const long double PI = acosl(-1.0L);

using namespace std;

void scans(string& str) {
	char c;
	str = "";
	scanf("%c", &c);
	if (c == '\n')scanf("%c", &c);
	while (c != '\n' && c != -1 && c != ' ') {
		str += c;
		scanf("%c", &c);
	}
}

void scanc(char& str) {
	char c;
	scanf("%c", &c);
	if (c == -1)return;
	while (c == '\n') {
		scanf("%c", &c);
	}
	str = c;
}

double acot(double x) {
	return PI / 2 - atan(x);
}

ll LSB(ll n) { return (n & (-n)); }

/*-----------------------------------------ここからコード-----------------------------------------*/


template<typename T>
vector<T> dijkstra(const vector<vector<pair<int, T>>>& graph, const int& v, const int& n, const T inf) {
	priority_queue<pair<T, int>, vector<pair<T, int>>, greater<pair<T, int>>> priq;
	vector<T> res(n);
	fill(all(res), inf);
	priq.push({ 0, v });
	res[v] = 0;
	int top;
	while (!priq.empty()) {
		top = priq.top().second;
		priq.pop();
		for (const auto& aa : graph[top]) {
			if (res[top] + aa.second >= res[aa.first])continue;
			res[aa.first] = aa.second + res[top];
			priq.push({ res[aa.first], aa.first });
		}
	}
	return res;
}

int main() {

	int n, m, x, y;
	scanf("%d%d%d%d", &n, &m, &x, &y);
	--x, --y;
	vector<vector<pair<int, long double>>> graph(n);
	vector<pair<int, int>> xy(n);
	int p, q;
	rep(i, n) {
		scanf("%d%d", &p, &q);
		xy[i] = { p, q };
	}
	rep(i, m) {
		scanf("%d%d", &p, &q);
		--p; --q;
		long double a = xy[p].first, b = xy[p].second, c = xy[q].first, d = xy[q].second;
		graph[p].push_back({ q, sqrt((c - a) * (c - a) + (d - b) * (d - b)) });
	}
	auto ans = dijkstra<long double>(graph, x, n, numeric_limits<long double>::infinity());
	printLdb(ans[y]);

	Please AC;
}