#include <stdio.h>

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

unsigned sieve(unsigned n)
{
    register unsigned i, j, nr = 2;

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

        ++i;

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

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

    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;
}