#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
#define N 1000000
int p[N];
int main() {
	int i, j,n,cnt;
	for (i = 2; i <= sqrt(N); i++) if (!p[i]) for (j = i*i; j < N; j += i)p[j] = 1;
	while (cin >> n) {
		cnt = 0;
		for (i = 2; i <= n; i++) if (!p[i]) cnt++;
		cout << cnt << endl;
	}
	return 0;
}
### Prompt

In CPP, your task is to solve 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<algorithm>
#include<cmath>
using namespace std;
#define N 1000000
int p[N];
int main() {
	int i, j,n,cnt;
	for (i = 2; i <= sqrt(N); i++) if (!p[i]) for (j = i*i; j < N; j += i)p[j] = 1;
	while (cin >> n) {
		cnt = 0;
		for (i = 2; i <= n; i++) if (!p[i]) cnt++;
		cout << cnt << endl;
	}
	return 0;
}
```