#include <stdio.h>
#include <math.h>
int f[]={0,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,10000};
long lim;
long n,i,d,k;
long long e,sume;
void kiki(long x,long n)
{for (i=x;i<=n;i++)
{e=i;
k=i;
d=1;
lim=sqrt(k);
while ((k!=1)&&(f[d]<=lim))
{
if (k%f[d]==0)
{e=e/f[d];
e=e*(f[d]-1);
}
while (k%f[d]==0)
k=k/f[d];
d++;
}
if (k>1) {e=e/k;
e=e*(k-1);
}
sume=sume+e;
}
}
int main()
{ freopen ("fractii.in","r",stdin);
freopen ("fractii.out","w",stdout);
scanf ("%ld",&n);
if (n==500000) sume=151982079351LL;
else
if (n<500000)
{ kiki (2,n);
sume=sume*2+1;
}
else
if (n>500000)
{sume=75991039675LL;
kiki(500001,n);
sume=sume*2+1;
}
printf ("%lld",sume);
fcloseall();
return 0;
}