#!/usr/bin/env python
import os
import sys
from io import BytesIO, IOBase
from collections import defaultdict as ddic
from itertools import groupby


def solve():
    (T, S, D) = readlist()
    # A = readlist()
    # Start T, careful 18 to 6, D km to reach target
    careful = 0
    while D:
        delta = min(S, D)
        if T >= 18 or T < 6:
            careful += delta / S
        else:
            delta *= 3
            delta = min(delta, D)
        D -= delta
        T += 1
        T %= 24
    return careful


def main():
    T = 1
    # T = readint()

    for tc in range(T):
        ans = solve()
        print(ans)
        # print("YES" if ans else "NO")


# region fastio

BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._file = file
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")
readint = lambda: int(input())
readlist = lambda: list(map(int, input().split()))

# endregion

if __name__ == "__main__":
    main()