#include <iostream>
#include <algorithm>
#include <vector>
#include <deque>
#include <queue>
#include <set>
#include <map>
#include <limits>
#include <cmath>
#include <iomanip>
#include <functional>
#include <random>
#include <unordered_map>
using namespace std;
using ll = long long;

int main()
{
    ll T,S,D;
    cin >> T >> S >> D;
    double ans = 0;
    while(D > 0){
        if ( (0 <= T && T < 6) || (18 <= T && T < 24)){
            ans += min(1.0,1.0*D/S) ;
        }
        D -= min(D,S);
        T = (T+1) % 24;
    }
    cout << fixed << setprecision(12) << ans << endl;
    return 0;
}