#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#pragma GCC optimize("Ofast")
#define is_set(x, y) (a[x] & r[y])
#define set_bit(x, y) (a[x] &= ~r[y])

char r[8] = {0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80};

int main()
{
    int n, i, j, N, nr = 0, index;
    char a[250001] = {0}, aux;
    FILE *in=fopen("ciur.in","r");
    FILE *out=fopen("ciur.out","w");    
    fscanf(in,"%d",&N);

    memset(a, 0xff, 250001);
    n = sqrt(N) + 1;
    for (i = 3; i <= n; i += 2)
    {
        if (is_set(i>>3, i & 0x7)) {    
            for (j = i*i; j <= N; j += 2*i) {
            	index = (j>>3);
            	aux = a[index];
                set_bit(index, j & 0x7);
                if (a[index] != aux)
                    nr++;
            }
        }                                    
    }
    nr = (N +1)/2 - nr;
 
    fprintf(out,"%d",nr);
    fclose(in);
    fclose(out);
    return 0;
}