#!/usr/bin/env python3

from math import ceil

def reducetwo(n):
    c = 0
    while not n%2:
        n //= 2
        c += 1
    return n, c

def primes(n):
    sieve = [0] * (n//2)
    for p in range(3, n, 2):
        if sieve[p//2] > 0:
            continue
        for k in range(1, n//p+1, 2):
            sieve[(p*k)//2] += p + sieve[k//2] - sieve[(p*k)//2]
    return sieve


n = 2*10**7
k = 15*10**6
sieve = primes(n)
print("Primed.")
s = 0

for m in range(n, n-k, -1):
    if not m % 2:
        m, c = reducetwo(m)
        s += 2*c
    s += sieve[m//2]

print("Calculated.")

for m in range(2, k+1):
    if not m % 2:
        m, c = reducetwo(m)
        s -= 2*c
    s -= sieve[m//2]

print(s)