1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
#include <fstream>

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

long long s,n,i,j;

int qw[1000001];

int main()
{
    fin>>n;
    for(i=2;i<=n;i++)
        qw[i]=i-1;
    for(i=2;i<=n;i++)
    {
        s+=qw[i];
        for(j=i*2;j<=n;j+=i)
            qw[j]-=qw[i];
    }
    fout<<s*2+1<<'\n';
    return 0;
}