#include <cstdio>
using namespace std;
int n,x,v[1000005],i,j;
long long nr;
int main() {
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        v[i]=i-1;
    for(i=2;i<=n;i++) {
        x=v[i];
        for(j=i*2;j<=n;j+=i) {
                v[j]=v[j]-x;}
        nr+=x; }
    nr=2*nr+1;
    printf("%lld",nr);
return 0;}