#include<iostream>
#include<string.h>
using namespace std;
int n,ans;
bool a[1000000];
int main(){
	while(cin>>n){
		memset(a,true,sizeof(a));
		a[0]=false;
		a[1]=false;
		ans=0;
		for(int i=2;i<=n;i++){
			if(a[i])
				for(int j=2*i;j<=n;j+=i)
					a[j]=false;
		}
		for(int i=1;i<=n;i++)
			if(a[i]) ans++; 
		cout<<ans<<endl;
	}
} 

### Prompt

Develop a solution in CPP to the problem described below:

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<string.h>
using namespace std;
int n,ans;
bool a[1000000];
int main(){
	while(cin>>n){
		memset(a,true,sizeof(a));
		a[0]=false;
		a[1]=false;
		ans=0;
		for(int i=2;i<=n;i++){
			if(a[i])
				for(int j=2*i;j<=n;j+=i)
					a[j]=false;
		}
		for(int i=1;i<=n;i++)
			if(a[i]) ans++; 
		cout<<ans<<endl;
	}
} 

```