#include<iostream>
#include<vector>
using namespace std;
int main(){
	int n;
	vector<int> pri(1000000);
	for(int i=0;i<1000000;i++)
		pri[i]=1;
	pri[0]=0;
	pri[1]=0;
	for(int i=0;i*i<n;i++){
		if(pri[i]){
			for(int j=i*2;j<1000000;j+=i)
				pri[j]=0;
		}
	}
	
	
	while(cin>>n){
	int i=0,k=0;
	while(k<=n)
	if(pri[k++])
	i++;
	
		cout<<i<<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<vector>
using namespace std;
int main(){
	int n;
	vector<int> pri(1000000);
	for(int i=0;i<1000000;i++)
		pri[i]=1;
	pri[0]=0;
	pri[1]=0;
	for(int i=0;i*i<n;i++){
		if(pri[i]){
			for(int j=i*2;j<1000000;j+=i)
				pri[j]=0;
		}
	}
	
	
	while(cin>>n){
	int i=0,k=0;
	while(k<=n)
	if(pri[k++])
	i++;
	
		cout<<i<<endl;
	}
	return 0;
}
```