#include <iostream>
#include <algorithm>
using namespace std;

const int inf = 987654321;
vector<double> dp;
int h, a, d;

double nya(int damage) {
  if(dp[damage] != inf) { return dp[damage]; }
  if(damage >= h) { return dp[damage] = 0; }
  double r1 = nya(damage + a) + 1,
         r2 = nya(damage + d) + 3. / 2;
  return dp[damage] = min(r1, r2);
}

int main(void) {
  scanf("%d%d%d", &h, &a, &d);
  dp.assign(h+10, inf);
  double res = nya(0);
  printf("%lf\n", res);
  return 0;
}