import java.util.Scanner;/*** 计算小于N的质数数量* @author Turing**/
public class Main4 {public static void main( String[] args ) {Scanner sc = new Scanner(System.in);int [] arr = new int[100];int num = 0;while(sc.hasNextLine()){String str = sc.nextLine().trim();if(str.equals("")){break;}else{arr[num++] = Integer.valueOf(str);}}for (int i = 0; i < num; i++) {System.out.println(primesNum(arr[i]));}}public static int primesNum(int n){boolean[] num = new boolean[n];int number = 0;for (int i = 2; i < n; i++) {if(!num[i]){number++;for (int j = 2; i*j < n; j++) {num[i*j]=true;}}}return number;}
}

import java.util.Scanner;/*** 逆时针打印矩阵* @author Turing**/
public class Main3 {public static void main( String[] args ) {Scanner sc = new Scanner(System.in);String[] results = new String[100];int index = 0;while(sc.hasNextLine()){String str = sc.nextLine().trim();if(str.equals("")){break;}else{String[] strs = str.split(" ");int M = Integer.valueOf(strs[0]);int N = Integer.valueOf(strs[1]);int [][] matrix = new int [M][N];int value = 1;for (int i = 0; i < M; i++) {for (int j = 0; j < N; j++) {matrix[i][j] = value;value++;}}results[index++] = spiral(matrix, M, N);}}for (int i = 0; i < index; i++) {System.out.println(results[i]);}}public static String spiral(int[][] matrix,int M,int N){String result = "";if(M!=0){int row1 = 0;int row2 = M -1;int col1 = 0;int col2 = N-1;while(row1<=row2 && col1<=col2){for (int i = col2; i >=col1; i--) {result += matrix[row1][i] +" ";}for (int i = row1+1; i <=row2; i++) {result += matrix[i][col1] +" ";}if(row1<row2 && col1<col2){for (int i = col1+1; i < col2; i++) {result += matrix[row2][i] +" ";}for (int i = row2; i > row1; i--) {result += matrix[i][col2] +" ";}}row1++;row2--;col1++;col2--;}}return result.trim();}
}

import java.util.Scanner;/*** a + b > C* int64 int64 int64* [-2^36,-2^63-1]* @author Turing**/
public class Main2 {public static void main( String[] args ) {Scanner sc = new Scanner(System.in);boolean[] results = new boolean[100];int index = 0;while(sc.hasNextLine()){String str = sc.nextLine().trim();if(str.equals("")){break;}else{String[] strs = str.split(" ");long a = Long.valueOf(strs[0]);long b = Long.valueOf(strs[1]);long c = Long.valueOf(strs[2]);results[index++] = abc(a, b, c);}}for (int i = 0; i < index; i++) {System.out.println(results[i]);}}public static boolean abc(long a, long b, long c){if(a>0 && b>0 && a+b<0){return true;}if(a<0 && b<0 && a+b>0){return false;}return a+b>c?true:false;}
}