#include<iostream>
#include<vector>
int main(){
	int n;
	while(std::cin>>n){
		int ans=0;
		std::vector<int> vec(n+1);
		for(int i=0;i<=n;i++)vec[i]=1;
		vec[0]=vec[1]=0;
		for(int i=2;i<=n;i++){
			if(vec[i] == 1){
				ans++;
				for(int j = 2 * i ; j <= n ; j += i){
					vec[j]=0;
				}
			}
		}
		std::cout<<ans<<std::endl;
	}

	return 0;
}
### 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<vector>
int main(){
	int n;
	while(std::cin>>n){
		int ans=0;
		std::vector<int> vec(n+1);
		for(int i=0;i<=n;i++)vec[i]=1;
		vec[0]=vec[1]=0;
		for(int i=2;i<=n;i++){
			if(vec[i] == 1){
				ans++;
				for(int j = 2 * i ; j <= n ; j += i){
					vec[j]=0;
				}
			}
		}
		std::cout<<ans<<std::endl;
	}

	return 0;
}
```