//#include <bits/stdc++.h>
#include <assert.h>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <iterator>
using namespace std;

typedef signed long long ll;

#define pp(...) (void)printf(__VA_ARGS__)
#define For(x,to) for(x=0;x<(to);x++)
#define For2(x,arr) for(auto& x:arr)
#define For3(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define All(a) (a.begin()),(a.end())
#define Zeros(a) memset(a,0,sizeof(a))
#define Minus(a) memset(a,0xff,sizeof(a))

#define PI 3.14159265
#define EPS (1e-10)
#define EPS_eq(a,b) (abs((a)-(b)) < EPS)

#pragma GCC diagnostic ignored "-Wconversion"

//#define int long long

const int INF = 1000*1000;

int dxy[] = {0, 1, 0, -1, 0};

typedef pair<int, int> P;

void pp_int(int x){ printf("%d\n", x); };

signed main() {
    int h,a,d;cin>>h>>a>>d;
    if(h <= a){
        // 通常オンリー
        pp("1\n");
        return 0;
    }
    int mx = ceil((double)h / a);
    if (d <= a) {
        // 通常オンリー
        pp("%d\n", mx);
        return 0;
    }
    // 必殺オンリー
    double res = INF;
    // 必殺アンド通常
    for(double i=0;i<mx;i+=0.5){
        double t = i * (d * 2.0 / 3.0);
        if(t>=h){
            res = min(res, i);
            continue;
        }
        double normal = ceil((h - t) / a);
        res = min(res, i + normal);
    }
    printf("%lf\n", res);
    return 0;
}