import math
import bisect

N = int(input())

def SoE(x):
    if x < 2:
        return []
    
    l = [i for i in range(x + 1)]
    l[1] = 0
    
    for i in l:
        if i > math.sqrt(x):
            break
        if i == 0:
            continue
        for j in range(2 * i , x + 1, i):
            l[j] = 0
    
    return [i for i in l if i != 0]

def index(a, x):
    i = bisect.bisect_left(a, x)
    if i != len(a) and a[i] == x:
        return 2
    else:
        return 0

prime = SoE(N)
ans = 0
for l_i in prime:
    a = pow(l_i,2) - 2
    ans += index(prime,a)

print(ans - 1)