n = int(input())
primes = []
ans = 0
r = set()
pq = set()
count = [0]*(n+1)
for i in range(2,n+1):
    if count[i]:
        continue
    primes.append(i)
    for j in range(i,n+1,i):
        count[j] += 1

    r.add(i**2)
    pq.add(i)

    for j in r:
        if j-i in pq:
            if i == j-i:
                ans += 1
            else:
                ans += 2


print(ans)