#include <iostream>
#include <cmath>
#define MAX 1000000
using namespace std;

int main()
{	
	bool p[MAX];
	fill(p, p + MAX, 1);
	
	p[0] = p[1] = 0;
	for (int i = 2; i < sqrt(MAX) + 1; i++) {
		if (p[i]) {
			for (int j = i * 2; j < MAX; j += i)
				p[j] = 0;
		}
	}
	
	int n;
	while (cin >> n) {
		int sum = 0;
		while(n) sum += p[n--];
		cout << sum << endl;;
	}
		
	return 0;
}
### 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>
#include <cmath>
#define MAX 1000000
using namespace std;

int main()
{	
	bool p[MAX];
	fill(p, p + MAX, 1);
	
	p[0] = p[1] = 0;
	for (int i = 2; i < sqrt(MAX) + 1; i++) {
		if (p[i]) {
			for (int j = i * 2; j < MAX; j += i)
				p[j] = 0;
		}
	}
	
	int n;
	while (cin >> n) {
		int sum = 0;
		while(n) sum += p[n--];
		cout << sum << endl;;
	}
		
	return 0;
}
```