#include <stdio.h>

#define SIZE 125001
char ciur[SIZE];
int main()
{
    FILE *fin, *fout;
    fin = fopen( "ciur.in", "r" );
    fout = fopen( "ciur.out", "w" );
    int n, i, j, cnt = 1;
    fscanf( fin, "%d", &n );
    for ( i = 1; ( ( i * i ) << 1 ) + ( i << 1 ) <= n; i++ ){
      if ( ( ciur[i >> 3] & ( 1 << ( i & 7 ) ) ) == 0 ){
        for (j = ( ( i * i ) << 1 ) + ( i << 1 ); ( j << 1 ) + 1 <= n; j+= (i << 1) + 1 ){
          ciur[j >> 3] |= ( 1 << ( j & 7 ) );
        }
      }
    }
    for ( i = 1; ( i << 1 ) + 1 <= n; i++ ){
      if ( ( ciur[i >> 3] & ( 1 << (i & 7 ) ) ) == 0 ){
        cnt++;
      }
    }
    fprintf( fout, "%d", cnt );
    return 0;
}