#!/usr/bin/env python
import os
import sys
from io import BytesIO, IOBase
from collections import defaultdict
from itertools import *
import random
import math

# MOD = 998244353
MOD = 10**9 + 7


def solve():
    N = rint()
    if N % 3 == 0:
        return N // 3
    if N % 3 == 2:
        return N // 3 + 1
    if N == 4:
        return 2
    N -= 4
    return 2 + N // 3


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

    for tc in range(1, 1 + T):
        ans = solve()

        print(ans)
        # print(*ans)

        # print("Yes" if ans else "No")
        # print("YES" if ans else "NO")
        # print("Alice" if ans else "Bob")
        # print("First" if ans else "Second")
        # print("Case #{}: {}".format(tc, ans))
        # print(len(ans))
        # for row in ans: print(*row)


# 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")
rint = lambda: int(input())


def rlist():
    return list(map(int, input().split()))


def rgrid(n):
    return [rlist() for _ in range(n)]


# endregion

if __name__ == "__main__":
    main()