import java.math.BigDecimal; import java.math.MathContext; import java.util.Scanner; public class Main { int vl, vr; int d; int w; BigDecimal checkai() { BigDecimal vl = new BigDecimal(this.vl, MathContext.DECIMAL128); BigDecimal vr = new BigDecimal(this.vr, MathContext.DECIMAL128); BigDecimal d = new BigDecimal(this.d, MathContext.DECIMAL128); BigDecimal w = new BigDecimal(this.w, MathContext.DECIMAL128); return w.multiply(d).divide(vl.add(vr), MathContext.DECIMAL128); } double souteikai() { double vl = (double) this.vl; double vr = (double) this.vr; double d = (double) this.d; double w = (double) this.w; return w * d / (vl + vr); } double gokai() { double vl = (double) this.vl; double vr = (double) this.vr; double d = (double) this.d; double w = (double) this.w; double ans = 0; while (d > 1e-7) { double t = d / (w + vr); ans += w * t; d -= t * (vl + vr); double tmp = vr; vr = vl; vl = tmp; } return ans; } void run() { vl = sc.nextInt(); vr = sc.nextInt(); d = sc.nextInt(); w = sc.nextInt(); assert (1 <= vl && vl <= 1_000_000_000L); assert (1 <= vr && vr <= 1_000_000_000L); assert (1 <= d && d <= 1_000_000_000L); assert (1 <= w && w <= 1_000_000_000L); assert (Math.max(vl, vr) < w); BigDecimal s = checkai(); double u = souteikai(); assert (Math.abs(BigDecimal.valueOf(u).subtract(s).doubleValue()) < 1e-6); if (max(vl, vr, d, w) <= 1_000_000L) { double g = gokai(); assert (Math.abs(BigDecimal.valueOf(g).subtract(s).doubleValue()) < 1e-6); } System.out.println(s.toPlainString()); System.out.flush(); } Scanner sc = new Scanner(System.in); public static void main(String[] args) { new Main().run(); } long max(long... a) { long r = Long.MIN_VALUE; for (long v : a) { r = Math.max(r, v); } return r; } }