#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
int sum[1000005];
bool shai[1000005];
void dabiao(){
	for(int i=2;i<=1000000;i++){
		sum[i]=sum[i-1];
		if(!shai[i]){
			for(int j=2*i;j<=1000000;j+=i)
				shai[j]=1;
			sum[i]++;
		}
	}
}
int main()
{
	dabiao();
	int n;
	while(scanf("%d",&n)==1){
		printf("%d\n",sum[n]);
	}
}
### Prompt

Create a solution in Cpp for 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<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
int sum[1000005];
bool shai[1000005];
void dabiao(){
	for(int i=2;i<=1000000;i++){
		sum[i]=sum[i-1];
		if(!shai[i]){
			for(int j=2*i;j<=1000000;j+=i)
				shai[j]=1;
			sum[i]++;
		}
	}
}
int main()
{
	dabiao();
	int n;
	while(scanf("%d",&n)==1){
		printf("%d\n",sum[n]);
	}
}
```