#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(isInt){
        yoruTime += (itime / 24)*12;
        itime %= 24;
    }
    else{
        yoruTime += (int)(dtime / 24.0)*(12);
        dtime -= (int)(dtime / 24.0)*24;
    }

    if(iD % iS == 0){
        isInt = true;
        itime = iD/iS;
    }
    if(T < 6){
        debugP();
        while(T < 6){
            yoruTime++;
            T++;
        }
    }
    else if(18 <= T){
        debugP();
        while(T < 24){
            yoruTime++;
            T++;
        }
        T = 0;
        while(T < 6){
            yoruTime++;
            T++;
        }
    }
    else{
        debugP();
        while(T < 18){
            T++;
            yoruTime++;
        }
    }

    debugVL(yoruTime);

    debugV(itime);
    debugVL(dtime);
    double ans = 0.0;
    if(isInt){
        debugP();
        ans = min(yoruTime, itime);
    }
    else{
        debugP();
        ans = min((double)yoruTime, dtime);
    }

    cout << ans << endl;
}