#include <iostream>
using namespace std;
int main(int argc, char *argv[]){
	int n;
	while(cin>>n){
		bool check[999999]={false};
		int count=0;
		for(int i=2;i<=n;i++){
			if(!check[i]){
				for (int j = 1; i*j <= n;j++){
					check[i*j]=true;
				}
				count++;
			}
		}
		cout<<count<<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>
using namespace std;
int main(int argc, char *argv[]){
	int n;
	while(cin>>n){
		bool check[999999]={false};
		int count=0;
		for(int i=2;i<=n;i++){
			if(!check[i]){
				for (int j = 1; i*j <= n;j++){
					check[i*j]=true;
				}
				count++;
			}
		}
		cout<<count<<endl;
	}
	return 0;
}
```