#include <cstdio>

int v[31260];

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

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

    for(int i = 1; ((i * i) << 1) + (i << 1) <= N; ++i)

        if(!(v[i >> 5] & (1 << (i & 31))))

            for(int j = ((i * i) << 1) + (i << 1); j << 1 < N; j += (i << 1) + 1)

                v[j >> 5] |= (1 << (j & 31));

    int p = 1;

    for(int i = 1; i << 1 < N; ++i)

        if(!(v[i >> 5] & (1 << (i & 31)))) ++p;


    printf("%d", p);

    return 0;
}