#include <cstdio>
using namespace std;
FILE *f, *g;
long long s;
int i,j,n,v[1000005];
int main()
{f=fopen ("fractii.in","r");
g=fopen ("fractii.out","w");
fscanf (f,"%d",&n);
for (i=2;i<=n;++i)
{if (v[i]==0)
{v[i]=i-1;
for (j=i*2;j<=n;j=j+i)
{if (v[j]==0)
v[j]=j/i*(i-1);
else
v[j]=v[j]/i*(i-1);
}
}
s=s+v[i]*2;
}
fprintf(g,"%lld",s+1);
return 0;
}