#include<iostream>
#include<vector>
using namespace std;
 int main(){
    int n,cnt;
  while(cin >> n){
    cnt=0;
    vector<bool>m(n+1,true);
    for(int i=2;i*i<=n;i++)
         if(m[i]) for(int j=i+i;j<=n;j+=i)  m[j]=false;        
    for(int i=2;i<=n;i++)
            if(m[i]) cnt++;
    cout << cnt << endl;  
  } 
  return 0;
}
### Prompt

Please provide a Cpp coded solution 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<iostream>
#include<vector>
using namespace std;
 int main(){
    int n,cnt;
  while(cin >> n){
    cnt=0;
    vector<bool>m(n+1,true);
    for(int i=2;i*i<=n;i++)
         if(m[i]) for(int j=i+i;j<=n;j+=i)  m[j]=false;        
    for(int i=2;i<=n;i++)
            if(m[i]) cnt++;
    cout << cnt << endl;  
  } 
  return 0;
}
```