Description

Input

Output

Sample Input

1
2
4
6

Sample Output

3
5
13
25

这个题目就是想说明，SB树和Farey序列的关系。

代码：

#include
#include
using namespace std;

long long phi[1000001];	

void get_phi()
{
	for (int i = 1; i <= 1000000; i++)phi[i] = i;
	for (int i = 2; i <= 1000000; i++)
	{
	if (phi[i] == i)for (int j = i; j <= 1000000; j += i)phi[j] = phi[j] / i*(i - 1);
	phi[i] += phi[i - 1];	
	}
}

int main()
{
	get_phi();
	int n;
	while (scanf("%d",&n)!=-1)printf("%llu\n", phi[n]*2+ 1);
	return 0;
}