import std.conv, std.functional, std.range, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons; import core.bitop; class EOFException : Throwable { this() { super("EOF"); } } string[] tokens; string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; } int readInt() { return readToken.to!int; } long readLong() { return readToken.to!long; } real readReal() { return readToken.to!real; } bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } } bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } } int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; } int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); } int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); } void main() { try { for (; ; ) { const N = readInt(); const M = readInt(); const S = readInt() - 1; const T = readInt() - 1; auto X = new real[N]; auto Y = new real[N]; foreach (u; 0 .. N) { X[u] = readReal(); Y[u] = readReal(); } auto A = new int[M]; auto B = new int[M]; foreach (i; 0 .. M) { A[i] = readInt() - 1; B[i] = readInt() - 1; } auto G = new int[][N]; foreach (i; 0 .. M) { G[A[i]] ~= i; G[B[i]] ~= i; } alias Entry = Tuple!(real, "c", int, "u"); BinaryHeap!(Array!Entry, "a > b") que; auto dist = new real[N]; auto vis = new bool[N]; dist[] = real.infinity; dist[S] = 0.0L; que.insert(Entry(0.0L, S)); for (; !que.empty; ) { const c = que.front.c; const u = que.front.u; que.removeFront; if (!vis[u]) { vis[u] = true; foreach (i; G[u]) { const v = A[i] ^ B[i] ^ u; if (!vis[v]) { const cc = c + sqrt((X[v] - X[u])^^2 + (Y[v] - Y[u])^^2); if (chmin(dist[v], cc)) { que.insert(Entry(cc, v)); } } } } } writefln("%.12f", dist[T]); } } catch (EOFException e) { } }