def primeset(N): #N以下の素数をsetで求める.エラトステネスの篩O(√Nlog(N))
    lsx = [1]*(N+1)
    for i in range(2,int(-(-N**0.5//1))+1):
        if lsx[i] == 1:
            for j in range(i,N//i+1):
                lsx[j*i] = 0
    setprime = set()
    for i in range(2,N+1):
        if lsx[i] == 1:
            setprime.add(i)
    return setprime
    
N = int(input())
setp = primeset(N)
lsp = list(setp)
lsp.sort()
P =len(lsp)
maxp = lsp[-1]
cnt = 0
for k in range(P):
    if lsp[k] ** 2 > maxp*2:
        break
    for j in range(P):
        if (lsp[k]**2 - lsp[j]) in setp:
            cnt += 1
print(cnt)