N = int(input())
if N <= 1:
    print(0)
    exit(0)

import math
P = [2]
for k in range(3,N+1):
    f = 1
    for l in range(2,int(math.sqrt(k))+1):
        if k % l == 0:
            f = 0
            break
    if f==1:
        P.append(k)

P = sorted(P)
R = []
for e in P:
    if e*e <= N*2:
        R.append(e*e)
    else:
        break

l = len(P)
ans = 1
for k in range(1,l):
    if 2+P[k] in R:
        ans += 2
print(ans)