import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int H = sc.nextInt();
    int A = sc.nextInt();
    int D = sc.nextInt();
    double ans = (H + A - 1) / A;
    if(A < D) {
      double[] dp = new double[H + 1];
      for(int i = 1; i <= A; i++) {
        dp[i] = 1;
      }
      for(int i = A + 1; i <= D; i++) {
        dp[i] = 1.5;
      }
      for(int i = D + 1; i < H + 1; i++) {
        dp[i] = Math.min(1 + dp[i - A], 1.5 + dp[i - D]);
      }
      ans = dp[H];
    }
    System.out.println(ans);
  }
}