#include <stdio.h>
#include <string.h>
int main(void){
    int n,a,b;
    char x[1000000];
    while(~scanf("%d",&n)){
        memset(x,0,sizeof(x));
        for(a=2;a<=n/2;a++)for(b=a*2;b<=n;b+=a)x[b]=1;
        for(a=2,b=0;a<=n;a++)if(!x[a])b++;
        printf("%d\n",b);
    }
    return 0;
}
### 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 <stdio.h>
#include <string.h>
int main(void){
    int n,a,b;
    char x[1000000];
    while(~scanf("%d",&n)){
        memset(x,0,sizeof(x));
        for(a=2;a<=n/2;a++)for(b=a*2;b<=n;b+=a)x[b]=1;
        for(a=2,b=0;a<=n;a++)if(!x[a])b++;
        printf("%d\n",b);
    }
    return 0;
}
```