#include <iostream>
#include <vector>
using namespace std;

int eratos(int n) {
	int cnt = 0;
	vector<bool> is_prime(n+1,true);
	is_prime[0] = is_prime[1] = false;
	for (auto i = 2; i <= n; i++) {
		if (is_prime[i]) {
			++cnt;
			for (auto j = 2*i; j <= n; j += i)
				is_prime[j] = false;
		}
	}
	return cnt;
}

int main() {
	for (int n; cin>>n; cout<<eratos(n)<<endl);
	return 0;
}
### Prompt

Please provide a CPP coded solution 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>
using namespace std;

int eratos(int n) {
	int cnt = 0;
	vector<bool> is_prime(n+1,true);
	is_prime[0] = is_prime[1] = false;
	for (auto i = 2; i <= n; i++) {
		if (is_prime[i]) {
			++cnt;
			for (auto j = 2*i; j <= n; j += i)
				is_prime[j] = false;
		}
	}
	return cnt;
}

int main() {
	for (int n; cin>>n; cout<<eratos(n)<<endl);
	return 0;
}
```