use std::{collections::BinaryHeap, cmp::Reverse};

const INF: f64 = (1usize << 60) as f64;

#[derive(PartialEq, PartialOrd, Clone, Debug)]
struct Sortable<T>(T);
 
impl<T: PartialEq> Eq for Sortable<T> {}
impl<T: PartialOrd> Ord for Sortable<T> {
    fn cmp(&self, other: &Sortable<T>) -> std::cmp::Ordering {
        self.0.partial_cmp(&other.0).unwrap()
    }
}


fn dijkstra(start: usize, paths: &Vec<Vec<(usize, f64)>>) -> Vec<f64> {
    let n = paths.len();
    let mut que = BinaryHeap::new();
    que.push((Reverse(Sortable(0.)), start));
    let mut costs = vec![INF; n];
    costs[start] = 0.;
    while let Some((Reverse(Sortable(cost)), u)) = que.pop() {
        if cost > costs[u] { continue; }
        for &(v, w) in paths[u].iter() {
            if costs[u] + w < costs[v] {
                costs[v] = costs[u] + w;
                que.push((Reverse(Sortable(costs[v])), v));
            }
        }
    }
    costs
}

fn calc(a: (isize, isize), b: (isize, isize)) -> f64 {
    (((a.0 - b.0) as f64).powf(2.) + ((a.1 - b.1) as f64).powf(2.)).sqrt()
}

fn main() {
    let mut nm = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nm[0];
    let m = nm[1];
    let mut temp = String::new();
    std::io::stdin().read_line(&mut temp).ok();
    let temp: Vec<usize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let x = temp[0]-1;
    let y = temp[1]-1;
    let points = (0..n).map(|_| {
            let mut temp = String::new();
            std::io::stdin().read_line(&mut temp).ok();
            let temp: Vec<isize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
            (temp[0], temp[1])
        })
        .collect::<Vec<_>>();
    let mut paths = vec![vec![]; n];
    for _ in 0..m {
        let mut temp = String::new();
        std::io::stdin().read_line(&mut temp).ok();
        let temp: Vec<usize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
        let u = temp[0]-1;
        let v = temp[1]-1;
        let dist = calc(points[u], points[v]);
        paths[u].push((v, dist));
        paths[v].push((u, dist));
    }

    let dists = dijkstra(x, &paths);
    println!("{}", dists[y]);
}