#include <stdio.h>
unsigned char ciur[ ( 1 << 17 ) ];

int main()
{
    int n;

    FILE *fin = fopen( "ciur.in", "r" );
    fscanf( fin, "%d", &n );
    fclose( fin );

    int no = 1;
    for( int i = 3; i <= n; i += 2 ){
        if( ( ciur[ i >> 4 ] & ( 1 << ( ( i >> 1 ) & 7 ) ) ) ) continue;
            ++no;
            for( int j = i + i + i; j <= n; j += i + i )
                ciur[ j >> 4 ] |= 1 << ( ( j >> 1 ) & 7 );
        }

    FILE *fout = fopen( "ciur.out", "w" );
    fprintf( fout, "%d\n", no );
    fclose( fout );
    return 0;
}