#include <iostream>
#include <bitset>
using namespace std;
bitset<1000000> p;
int main(){
  p.flip();
  p[0] = 0;
  p[1] = 0;
  for(int i = 2; i < 1000; ++i){
    if(p[i]){
      for(int j = 2*i; j < 1000000; j += i) p[j] = 0;
    }
  }
  int n;
  while(cin >> n){
    int ret = 0;
    for(int i = 2; i <= n; ++i) ret += p[i];
    cout << ret << '\n';
  }
  return 0;
}

### Prompt

Generate 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 <bitset>
using namespace std;
bitset<1000000> p;
int main(){
  p.flip();
  p[0] = 0;
  p[1] = 0;
  for(int i = 2; i < 1000; ++i){
    if(p[i]){
      for(int j = 2*i; j < 1000000; j += i) p[j] = 0;
    }
  }
  int n;
  while(cin >> n){
    int ret = 0;
    for(int i = 2; i <= n; ++i) ret += p[i];
    cout << ret << '\n';
  }
  return 0;
}

```