import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.util.StringTokenizer; public class Main { private static class FastScanner { private BufferedReader reader = null; private StringTokenizer tokenizer = null; public FastScanner(InputStream in) { reader = new BufferedReader(new InputStreamReader(in)); tokenizer = null; } public String next() { if (tokenizer == null || !tokenizer.hasMoreTokens()) { try { tokenizer = new StringTokenizer(reader.readLine()); } catch (IOException e) { throw new RuntimeException(e); } } return tokenizer.nextToken(); } public String nextLine() { if (tokenizer == null || !tokenizer.hasMoreTokens()) { try { return reader.readLine(); } catch (IOException e) { throw new RuntimeException(e); } } return tokenizer.nextToken("\n"); } public long nextLong() { return Long.parseLong(next()); } public int nextInt() { return Integer.parseInt(next()); } public double nextDouble() { return Double.parseDouble(next()); } public int[] nextIntArray(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) a[i] = nextInt(); return a; } public long[] nextLongArray(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) a[i] = nextLong(); return a; } } public static void main(String[] args) { FastScanner sc = new FastScanner(System.in); double p = sc.nextDouble(); System.out.println(p/(1-p)); } }