#include<iostream>
#include<cstring> 
using namespace std;
bool a[10000000];
int main()
{
	int n;
	while(cin>>n)
	{	
		int js=0;
		for (int i=2;i<=n;i++)
		  if (!a[i]) {js++;for (int j=i+i;j<=n;j+=i) a[j]=true;}
		cout<<js<<endl;   
	}
} 

### Prompt

Construct a cpp code solution to the problem outlined:

Write a program which reads an integer n and prints the number of prime numbers which are less than or equal to n. A prime number is a natural number which has exactly two distinct natural number divisors: 1 and itself. For example, the first four prime numbers are: 2, 3, 5 and 7.



Input

Input consists of several datasets. Each dataset has an integer n (1 ≤ n ≤ 999,999) in a line.

The number of datasets is less than or equal to 30.

Output

For each dataset, prints the number of prime numbers.

Example

Input

10
3
11


Output

4
2
5

### Response

```cpp
#include<iostream>
#include<cstring> 
using namespace std;
bool a[10000000];
int main()
{
	int n;
	while(cin>>n)
	{	
		int js=0;
		for (int i=2;i<=n;i++)
		  if (!a[i]) {js++;for (int j=i+i;j<=n;j+=i) a[j]=true;}
		cout<<js<<endl;   
	}
} 

```