from collections import defaultdict
from sys import stdin

def primes235(limit):
    yield 2; yield 3; yield 5
    if limit < 7: return
    modPrms = [7,11,13,17,19,23,29,31]
    gaps = [4,2,4,2,4,6,2,6,4,2,4,2,4,6,2,6]
    ndxs = [0,0,0,0,1,1,2,2,2,2,3,3,4,4,4,4,5,5,5,5,5,5,6,6,7,7,7,7,7,7]
    lmtbf = (limit + 23) // 30 * 8 - 1
    lmtsqrt = (int(limit ** 0.5) - 7)
    lmtsqrt = lmtsqrt // 30 * 8 + ndxs[lmtsqrt % 30]
    buf = [True] * (lmtbf + 1)
    for i in range(lmtsqrt + 1):
        if buf[i]:
            ci = i & 7; p = 30 * (i >> 3) + modPrms[ci]
            s = p * p - 7; p8 = p << 3
            for j in range(8):
                c = s // 30 * 8 + ndxs[s % 30]
                buf[c::p8] = [False] * ((lmtbf - c) // p8 + 1)
                s += p * gaps[ci]; ci += 1
    for i in range(lmtbf - 6 + (ndxs[(limit - 7) % 30])):
        if buf[i]: yield (30 * (i >> 3) + modPrms[i & 7])

def main():
    N = int(input())

    primes = list(primes235(N))
    r2 = defaultdict(int)
    for i in primes:
        r2[i*i] = 1

    ans = 0
    for i in primes:
        if r2[2+i]:
            if i == 2:
                ans += 1
            else:
                ans += 2
    print(ans)

input = lambda: stdin.readline()
main()