#![allow(non_snake_case)]
#![allow(dead_code)]
#![allow(unused_macros)]
#![allow(unused_imports)]

use std::str::FromStr;
use std::io::*;
use std::collections::*;
use std::cmp::*;

use std::f64::INFINITY;

struct Scanner<I: Iterator<Item = char>> {
    iter: std::iter::Peekable<I>,
}

macro_rules! exit {
    () => {{
        exit!(0)
    }};
    ($code:expr) => {{
        if cfg!(local) {
            writeln!(std::io::stderr(), "===== Terminated =====")
                .expect("failed printing to stderr");
        }
        std::process::exit($code);
    }}
}

impl<I: Iterator<Item = char>> Scanner<I> {
    pub fn new(iter: I) -> Scanner<I> {
        Scanner {
            iter: iter.peekable(),
        }
    }

    pub fn safe_get_token(&mut self) -> Option<String> {
        let token = self.iter
            .by_ref()
            .skip_while(|c| c.is_whitespace())
            .take_while(|c| !c.is_whitespace())
            .collect::<String>();
        if token.is_empty() {
            None
        } else {
            Some(token)
        }
    }

    pub fn token(&mut self) -> String {
        self.safe_get_token().unwrap_or_else(|| exit!())
    }

    pub fn get<T: FromStr>(&mut self) -> T {
        self.token().parse::<T>().unwrap_or_else(|_| exit!())
    }

    pub fn vec<T: FromStr>(&mut self, len: usize) -> Vec<T> {
        (0..len).map(|_| self.get()).collect()
    }

    pub fn mat<T: FromStr>(&mut self, row: usize, col: usize) -> Vec<Vec<T>> {
        (0..row).map(|_| self.vec(col)).collect()
    }

    pub fn char(&mut self) -> char {
        self.iter.next().unwrap_or_else(|| exit!())
    }

    pub fn chars(&mut self) -> Vec<char> {
        self.get::<String>().chars().collect()
    }

    pub fn mat_chars(&mut self, row: usize) -> Vec<Vec<char>> {
        (0..row).map(|_| self.chars()).collect()
    }

    pub fn line(&mut self) -> String {
        if self.peek().is_some() {
            self.iter
                .by_ref()
                .take_while(|&c| !(c == '\n' || c == '\r'))
                .collect::<String>()
        } else {
            exit!();
        }
    }

    pub fn peek(&mut self) -> Option<&char> {
        self.iter.peek()
    }
}

#[derive(PartialEq)]
struct MinFloat(f64);

impl Eq for MinFloat {}

impl PartialOrd for MinFloat {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        other.0.partial_cmp(&self.0)
    }
}

impl Ord for MinFloat {
    fn cmp(&self, other: &Self) -> Ordering {
        other.0.partial_cmp(&self.0).unwrap()
    }
}

fn main() {
    let cin = stdin();
    let cin = cin.lock();
    let mut sc = Scanner::new(cin.bytes().map(|c| c.unwrap() as char));
    let N: usize = sc.get();
    let M: usize = sc.get();
    let X: usize = sc.get::<usize>()-1;
    let Y: usize = sc.get::<usize>()-1;
    let mut p: Vec<f64> = vec![0.; N];
    let mut q: Vec<f64> = vec![0.; N];
    for i in 0..N {
        p[i] = sc.get();
        q[i] = sc.get();
    }
    let mut adj = vec![Vec::new(); N];
    for _ in 0..M {
        let P: usize = sc.get::<usize>()-1;
        let Q: usize = sc.get::<usize>()-1;
        let cost = (p[P] - p[Q]).hypot(q[P] - q[Q]);
        adj[P].push((Q, cost));
        adj[Q].push((P, cost));
    }
    let mut bh = BinaryHeap::new();
    bh.push((MinFloat(0.), X));
    let mut dp = vec![INFINITY; N];
    dp[X] = 0.;
    while let Some((MinFloat(cost), now)) = bh.pop() {
        if dp[now] < cost {
            continue;
        }
        for &(to, cost) in &adj[now] {
            if dp[to] > dp[now] + cost {
                dp[to] = dp[now] + cost;
                bh.push((MinFloat(dp[to]), to));
            }
        }
    }
    println!("{}", dp[Y]);
}