#include <stdio.h>
#define N_MAX 2000001

typedef char bool;

bool ciur[ N_MAX + 1 ];

int main( ) {
    FILE * fin, * fout;
    fin = fopen( "ciur.in", "r" );
    fout = fopen( "ciur.out", "w" );

    int N;
    fscanf( fin, "%d", &N );

    int i;
    for( i = 2; i <= N; i ++ ) {
        if( !ciur[ i ] ) {
            int j;
            for( j = 2 * i; j <= N; j += i ) {
                ciur[ j ] = 1;
            }
        }
    }

    int num = 0;
    for( i = 1; i <= N; i ++ ) {
        num += ciur[ i ];
    }
    fprintf( fout, "%d\n", N - num - 1 );

    fclose( fin );
    fclose( fout );
}