#include <iostream>
#include <iomanip>
using namespace std;

int main() {
    int t, s, d;
    cin >> t >> s >> d;

    double time = (double) d / s;
    if (time <= 1.0 * (24 - t)) {
        cout << fixed << setprecision(10) << time << endl;
    } else {
        cout << fixed << setprecision(10) << (double)(d - s * (24 - t)) / (2 * s) + (24 - t) << endl;
    }

    return 0;
}