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

Your task is to create 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<vector>
using namespace std;
int main(void){
  int n;
while(cin>>n){
  vector<bool> nature(n,true);
  nature[0]=nature[1]=false;
  for(int i=0;i*i<=n;i++){
if(nature[i]){
  for(int j=2;j<=n/i;j++)
  nature[i*j]=false;
}
  }
int count=0;
for(int i=0;i<=n;i++)
if(nature[i])
count++;
cout<<count<<endl;
}
return 0;
}
```