#include<stdio.h>
#include<stdlib.h>

#define MIN(a,b) ((a)<(b)?(a):(b))

void run(void){
  int h,a,d;
  scanf("%d%d%d",&h,&a,&d);

  if(d<=a){
    printf("%d\n",(h+a-1)/a);
    return;
  }

  double *e=(double *)malloc(sizeof(double)*(h+1));
  e[0]=0;
  int i;
  for(i=1;i<=a;i++){
    e[i]=1;
  }
  for(i=a+1;i<=d;i++){
    e[i]=MIN(1+e[i-a],1.5);
  }
  for(i=d+1;i<=h;i++){
    e[i]=MIN(1+e[i-a],1.5+e[i-d]);
  }
  printf("%.2lf\n",e[h]);
  free(e);
  return;
}

int main(void){
  run();
  return 0;
}