#include <bits/stdc++.h>

using namespace std;

int main(void) {
  int H, A, D;
  cin >> H >> A >> D;
  
  double dp[10010];
  dp[0] = 0;
  for (int i = 1; i <= H; i++) {
    dp[i] = min(dp[max(0, i - A)] + 1, dp[max(0, i - D)] + 1.5);
  }
  printf("%.10f\n", dp[H]);

  return 0;
}