#include <bits/stdc++.h>
using namespace std;

using i64 = int64_t;
using ui64 = uint64_t;

#ifdef LOCAL_DEBUG
    #define debug(X) std::cerr << X << " "
    #define debugV(X) std::cerr << #X << " = " << X << ", "
    #define debugVL(Y) std::cerr << #Y << " = " << Y << '\n'
    #define debugWL(Z) std::cerr << #Z << '\n'
    #define debugP() std::cerr << "Line:" << __LINE__ << '\n'
#else
    #define debug(X)
    #define debugV(X)
    #define debugVL(Y)
    #define debugWL(Z)
    #define debugP()
#endif

int main() {
    cout << setprecision(17);

    i64 T, iS, iD;
    cin >> T >> iS >> iD;
    double S = iS, D = iD;



    i64 itime = iD/iS;
    double dtime = D/S;
    bool isInt = false;
    i64 yoruTime = 0;
    if(iD % iS == 0){
        isInt = true;
        itime = iD/iS;
    }
    if(isInt){
        debugWL(is int);
        yoruTime += (itime / 24)*12;
        itime %= 24;
        dtime = itime;
    }
    else{
        yoruTime += ((int)dtime / 24)*(12);
        while(24 <= dtime){
            dtime -= 24.0;
        }
    }
    double ans = yoruTime;
    yoruTime = 0;
    debugV(itime);
    debugVL(dtime);

    if(T < 6){
        debugP();
        while(T < 6){
            yoruTime++;
            T++;
        }
    }
    else if(18 <= T){
        debugP();
        int cnt = 0;
        while(T < 24){
            yoruTime++;
            T++;
        }
        T = 0;
        while(T < 6){
            yoruTime++;
            T++;
        }
    }
    else{
        debugP();
        int cnt = 0;
        while(T < 18){
            if(cnt >= (int)dtime){
                break;
            }
            cnt++;
            T++;
        }
        while(T < 24){
            if(cnt >= (int)dtime){
                break;
            }
            cnt++;
            yoruTime++;
            T++;
        }
        T = 0;
        while(T < 6){
            if(cnt >= (int)dtime){
                break;
            }
            cnt++;
            yoruTime++;
            T++;
        }
    }

    debugVL(yoruTime);

    debugV(itime);
    debugVL(dtime);
    if(isInt){
        debugP();
        ans += min(yoruTime, itime);
    }
    else{
        debugP();
        ans += min((double)yoruTime, dtime);
    }

    cout << ans << endl;
}