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#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
unsigned long long n,m,i,j,k,sol,x,p;
int main()
{
f>>n;
for(i=2;i<=n;i++)
{
int nr=i;
x=i;
j=2;
while(j*j<=x)
{
p=0;
while(x%j==0)
{
p++;
x=x/j;
}
if(p!=0)
{
nr=nr*(j-1)/j;
}
j++;
}
if(x>1)
{
nr=nr*(x-1)/x;
}
sol+=nr*2;
}
g<<sol+1;
return 0;
}