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

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

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

       for (i = 2; i <= n; i++)
       {
           if ((a[i >> 3] & r[i & 0x7]) == 0)
           {
              nr++;    
              for (j = (i << 1); j <= n; j += i)
                  a[j >> 3] |= r[j & 0x7];
           }                                    
       }
 
       fprintf(out,"%d",nr);
       fclose(in);
       fclose(out);
       return 0;
}