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// Online C++ compiler to run C++ program online
#include <iostream>
using namespace std;
int fi[1000000];
long long int s;
int main() {
// Write C++ code here
//std::cout << "Hello world!";
int n,i,j;
ifstream fin ("fractii.in");
fin >> n;
fin.close();
if(n>=2)
s=1;
for(i=4;i<=n;i+=2)
fi[i]=i/2;
for(i=3;i<=n;i++)
if(fi[i]==0)
{
s+=i-1;
for (j=2*i;j<=n;j+=i)
{
if(fi[j]==0)
fi[j]=j;
fi[j]/=i;
fi[j]*=i-1;
}
}
else
s+=fi[i];
s*=2;
s+=1;
ofstream fout ("fractii.out");
fout <<s;
fout.close();
return 0;
}