#include <bits/stdc++.h>
using namespace std;

int main(){
	int n;
	while(cin>>n){
		int cnt=0;
		vector<bool> v(n+1,true);
		for(int i=2; i<=sqrt(n); i++){
			if(v[i]){
				for(int j=2; i*j<=n;j++){
						v[i*j]=false;
				}
			}
		}
		for(int i=2;i<=n;i++){
			if(v[i])
				cnt++;
		}
		cout << cnt << endl;
	}
}
### Prompt

Your challenge is to write 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 <bits/stdc++.h>
using namespace std;

int main(){
	int n;
	while(cin>>n){
		int cnt=0;
		vector<bool> v(n+1,true);
		for(int i=2; i<=sqrt(n); i++){
			if(v[i]){
				for(int j=2; i*j<=n;j++){
						v[i*j]=false;
				}
			}
		}
		for(int i=2;i<=n;i++){
			if(v[i])
				cnt++;
		}
		cout << cnt << endl;
	}
}
```