#include<iostream>

using namespace std;

bool sosu(int n)
{
	for(int i=2;i*i<=n;i++){
		if(n%i==0){
			return false;
		}
	}
	return true;
}

int main(void)
{
	int n;
	bool flag[1000000];
	for(int i=1;i<=999999;i++){
		flag[i]=sosu(i);
	}
	while(cin>>n){
		int ans=0;
		for(int i=2;i<=n;i++){
			if(flag[i])
				ans++;
		}
		cout<<ans<<endl;
	}
}
### Prompt

Please formulate a Cpp solution 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>

using namespace std;

bool sosu(int n)
{
	for(int i=2;i*i<=n;i++){
		if(n%i==0){
			return false;
		}
	}
	return true;
}

int main(void)
{
	int n;
	bool flag[1000000];
	for(int i=1;i<=999999;i++){
		flag[i]=sosu(i);
	}
	while(cin>>n){
		int ans=0;
		for(int i=2;i<=n;i++){
			if(flag[i])
				ans++;
		}
		cout<<ans<<endl;
	}
}
```