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

#pragma GCC optimize("Ofast")

#define is_set(x)  (a[x>>3] & r[x & 0x7])
#define set_bit(x) (a[x>>3] |= r[x & 0x7])

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);

    for (i = 3; i*i <= N; i += 2) {
        if (!is_set(i)) {    
            for (j = i*i; j <= N; j += 2*i) {
                if (!is_set(j)) {
                	set_bit(j);
                	nr++;
				}
            }
        }                                    
    }
 
    fprintf(out,"%d", (N+1)/2 - nr);
    fclose(in);
    fclose(out);
    return 0;
}