#include <stdio.h>

unsigned p[(2000000U >> 6U) + 1U]{};

unsigned sieve(unsigned n)
{
    register unsigned i, j, nr = 1U + (n > 2U);

    for(i = 2U; ((i * i) << 1U) + (i << 1U) < n - 3U; i += 2U)
    {
        if((p[i >> 5U] & (1U << (i & 31U))) == 0U)
        {
            for(j = ((i * i) << 1U) + (i << 1U); (j << 1U) < n; j += (i << 1U) + 1U)
            {
                p[j >> 5U] |= (1U << (j & 31U));
            }
        }

        ++i;

        if((p[i >> 5U] & (1U << (i & 31U))) == 0U)
        {
            for(j = ((i * i) << 1U) + (i << 1U); (j << 1U) < n; j += (i << 1U) + 1U)
            {
                p[j >> 5U] |= (1U << (j & 31U));
            }
        }
    }

    for(i = 2U; (i << 1U) < n - 2U; i += 3U)
    {
        nr += ((p[ i       >> 5U] & (1U << ( i       & 31U))) == 0U) +
              ((p[(i + 1U) >> 5U] & (1U << ((i + 1U) & 31U))) == 0U);
    }

    return nr;
}

int main()
{
    freopen("ciur.in", "r", stdin);
    freopen("ciur.out", "w", stdout);

    unsigned N; scanf("%d", &N);

    printf("%u ", sieve(N));

    return 0;
}