#include <iostream>
using namespace std;
const int maxn=1e6 + 10;
int p[maxn],inp[maxn],f[maxn],top;
void init(){
	for(int i=2;i<maxn;i++){
		if(!inp[i]){
			p[top++]=i;
		}
		for(int j=0;j<top && i*p[j]<maxn;j++){
			inp[i*p[j]]=1;
			if(!(i%p[j]))
				break;
		}
		f[i]=f[i-1]+1-inp[i];
	}
}
int main(){
	init();
	int n;
	while(cin>>n){
		cout<<f[n]<<endl;
	}
	return 0;
}
### Prompt

Generate 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>
using namespace std;
const int maxn=1e6 + 10;
int p[maxn],inp[maxn],f[maxn],top;
void init(){
	for(int i=2;i<maxn;i++){
		if(!inp[i]){
			p[top++]=i;
		}
		for(int j=0;j<top && i*p[j]<maxn;j++){
			inp[i*p[j]]=1;
			if(!(i%p[j]))
				break;
		}
		f[i]=f[i-1]+1-inp[i];
	}
}
int main(){
	init();
	int n;
	while(cin>>n){
		cout<<f[n]<<endl;
	}
	return 0;
}
```