from sys import stdin
import math
 
N = int(stdin.readline().rstrip())

def f(z):
    ok = -1
    ng = 10**4
    while abs(ok-ng)>1:
        d = (ok+ng)//2
        if d*d*z<=N:
            ok = d
        else:
            ng = d
    return ok

ans = 0
for i in range(1,N+1):
    ans += 2*math.floor((N/i)**0.5)-1
    #print(f(i),i)
print(ans)