#include<iostream>
#include<cstring>
#include<cmath>
using namespace std;

bool f[1000000];

int main(){
	int n;
	while(cin>>n){
		memset(f,0,n*sizeof(bool));
		int l=sqrt(n);
		for(int i=2;i<=l;i++){
			for(int j=2;j*i<=n;j++){
				f[j*i]=true;
			}
		}
		int cnt=0;
		for(int i=2;i<=n;i++) if(!f[i])cnt++;
		cout<<cnt<<endl;
	}
}
### Prompt

Please create a solution in Cpp to the following problem:

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>
#include<cmath>
using namespace std;

bool f[1000000];

int main(){
	int n;
	while(cin>>n){
		memset(f,0,n*sizeof(bool));
		int l=sqrt(n);
		for(int i=2;i<=l;i++){
			for(int j=2;j*i<=n;j++){
				f[j*i]=true;
			}
		}
		int cnt=0;
		for(int i=2;i<=n;i++) if(!f[i])cnt++;
		cout<<cnt<<endl;
	}
}
```