import sys
input = sys.stdin.readline
from math import sqrt

N=int(input())

X=[i for i in range(N+1)]
for i in range(1,N//4+1):
    if X[i]!=i:
        continue

    for j in range(2,N+1):
        if i*j*j<=N:
            X[i*j*j]=i
        else:
            break

ANS=0

for i in range(1,N+1):
    ANS+=int(sqrt(N//X[i]))

print(ANS)