#define REP(i,n) for(int i=0; i<(int)(n); i++)

#include <cstdio>
inline int getInt(){ int s; scanf("%d", &s); return s; }

#include <set>

using namespace std;

double dp[10000 + 1];

int main(){
  const int h = getInt();
  const int a = getInt();
  const int d = getInt();

  REP(i,h) dp[i] = 1000000;

  for(int i = h; i > 0; i--){
    dp[max(i - a, 0)] = min(dp[max(i - a, 0)], dp[i] + 1);
    dp[max(i - d, 0)] = min(dp[max(i - d, 0)], dp[i] + 1.5);
  }

  printf("%.1f\n", dp[0]);

  return 0;
}