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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll T, S, D;
    cin >> T >> S >> D;
    double T2 = double(D) / S, ans = 0;
    for(int i = 0; i < 10000000; i++){
        if(T2 <= 0) break;
        if((T + i) % 24 <= 18 && (T + i) % 24 + 1 <= 24){
            double add = min(1.0, T2);
            ans += add;
        }
        if((T + i) % 24 <= 0 && (T + i) % 24 + 1 <= 6){
            double add = min(1.0, T2);
            ans += add;
        }
        T2 -= 1;
    }
    cout << fixed << setprecision(15) << double(D) / S << '\n';
}