import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))

### ふるい
def hurui(n):
    """n以下の素数のリストを返す
    """
    not_prime = [0]*(n+1)
    for p in range(2,n+1):
        if not_prime[p]:
            continue
        for i in range(2*p, n+1, p):
            not_prime[i] = 1
#     return not_prime
    return [i for i in range(2,n+1) if not not_prime[i]]

n = int(input())
# ps = hurui(n)
vals = [0]*(n+1)
for i in range(1,n+1):
    if i*i>n:
        break
    vals[i*i] = i
v = 0
for i in range(1,n+1):
    if vals[i]==0:
        vals[i] = v
    else:
        v = vals[i]
xs = list(range(n+1))
not_prime = [0]*(n+1)
for p in range(2,n+1):
    if p*p>n:
        break
    if not_prime[p]:
        continue
    for i in range(2*p, n+1, p):
        not_prime[i] = 1
    pp = p*p
    for i in range(p*p, n+1, p*p):
        xs[i] //= pp
ans = 0
for a in range(1,n+1):
    ans += vals[n//xs[a]]
print(ans)