#include <stdio.h>
int main(){
	int i,j,n,num;
	bool prime[1000000];
	bool flag=true;
	for(i=0;i<999999;i++) prime[i]=true;
	while(scanf("%d",&n)!=EOF){
		num=0;
		for(i=2;i<n+1;i++){
				for(j=i*2;j<n+1;j=j+i) prime[j]=false;
		}
		for(i=2;i<n+1;i++){
			if(prime[i]==true) num++;
		}
		printf("%d\n",num);
	}
}
### Prompt

Develop a solution in cpp 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 <stdio.h>
int main(){
	int i,j,n,num;
	bool prime[1000000];
	bool flag=true;
	for(i=0;i<999999;i++) prime[i]=true;
	while(scanf("%d",&n)!=EOF){
		num=0;
		for(i=2;i<n+1;i++){
				for(j=i*2;j<n+1;j=j+i) prime[j]=false;
		}
		for(i=2;i<n+1;i++){
			if(prime[i]==true) num++;
		}
		printf("%d\n",num);
	}
}
```