import java.util.Arrays; import java.util.Comparator; import java.util.Scanner; import java.util.TreeSet; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); int m = sc.nextInt(); int x = sc.nextInt() - 1; int y = sc.nextInt() - 1; int[][] p = new int[n][]; for (int i = 0; i < n; i++) { p[i] = new int[] { Integer.parseInt(sc.next()), Integer.parseInt(sc.next()) }; } int[] from = new int[m]; int[] to = new int[m]; int[] w = new int[m]; for (int i = 0; i < m; i ++) { from[i] = Integer.parseInt(sc.next()) - 1; to[i] = Integer.parseInt(sc.next()) - 1; int dx = p[from[i]][0] - p[to[i]][0]; int dy = p[from[i]][1] - p[to[i]][1]; w[i] = dx * dx + dy * dy; } int[][][] g = packWU(n, from, to, w); double[] d = dijk(g, x); System.out.println(d[y]); } public static int[][][] packWU(int n, int[] from, int[] to, int[] w){ return packWU(n, from, to, w, from.length); } public static int[][][] packWU(int n, int[] from, int[] to, int[] w, int sup) { int[][][] g = new int[n][][]; int[] p = new int[n]; for(int i = 0;i < sup;i++)p[from[i]]++; for(int i = 0;i < sup;i++)p[to[i]]++; for(int i = 0;i < n;i++)g[i] = new int[p[i]][2]; for(int i = 0;i < sup;i++){ --p[from[i]]; g[from[i]][p[from[i]]][0] = to[i]; g[from[i]][p[from[i]]][1] = w[i]; --p[to[i]]; g[to[i]][p[to[i]]][0] = from[i]; g[to[i]][p[to[i]]][1] = w[i]; } return g; } public static double[] dijk(int[][][] g, int from) { int n = g.length; final double[] td = new double[n]; Arrays.fill(td, Integer.MAX_VALUE); TreeSet q = new TreeSet(new Comparator(){ public int compare(Integer a, Integer b) { if(td[a] - td[b] != 0)return Double.compare(td[a], td[b]); return a - b; } }); q.add(from); td[from] = 0; while(q.size() > 0){ int cur = q.pollFirst(); for(int i = 0;i < g[cur].length;i++){ int next = g[cur][i][0]; double nd = td[cur] + Math.sqrt(g[cur][i][1]); if(nd < td[next]){ q.remove(next); td[next] = nd; q.add(next); } } } return td; } }