#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main(){
    bool f[1000001];
    fill(f,f+1000001,true);
    f[0]=f[1]=false;
    for(int i=2;i*i<=1000001;i++)
        if(f[i])
            for(int j=i*i;j<=1e6;j+=i)
                f[j]=false;

    int n;
    while(cin>>n)
        cout<<count(f,f+n+1,true)<<endl;

}
### Prompt

Please formulate 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>
#include<algorithm>
#include<vector>
using namespace std;
int main(){
    bool f[1000001];
    fill(f,f+1000001,true);
    f[0]=f[1]=false;
    for(int i=2;i*i<=1000001;i++)
        if(f[i])
            for(int j=i*i;j<=1e6;j+=i)
                f[j]=false;

    int n;
    while(cin>>n)
        cout<<count(f,f+n+1,true)<<endl;

}
```