#include <cstdio>
#include <bitset>
using namespace std;
int c[999999]={0,1};
int main() {
	bitset<499999> b;
	int i,j,n=3;
	for(i=0;n*n<=999999;i++,n+=2) {
		if(b[i])continue;
		for(j=i+n;j<499999;j+=n)b[j]=1;
	}
	for(i=0,n=3;i<=499998;i++,n+=2) {
		if(!b[i])c[n-1]=c[n]=c[n-2]+1;
		else c[n-1]=c[n]=c[n-2];
	}
	while(scanf("%d",&n)!=EOF) {
		printf("%d\n",c[n-1]);
	}
}
### Prompt

Construct a CPP code solution to the problem outlined:

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 <bitset>
using namespace std;
int c[999999]={0,1};
int main() {
	bitset<499999> b;
	int i,j,n=3;
	for(i=0;n*n<=999999;i++,n+=2) {
		if(b[i])continue;
		for(j=i+n;j<499999;j+=n)b[j]=1;
	}
	for(i=0,n=3;i<=499998;i++,n+=2) {
		if(!b[i])c[n-1]=c[n]=c[n-2]+1;
		else c[n-1]=c[n]=c[n-2];
	}
	while(scanf("%d",&n)!=EOF) {
		printf("%d\n",c[n-1]);
	}
}
```