#include<stdio.h>
int n,j,i;
long long v[1000001],s;
int main() {
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
 
    scanf("%d",&n);
 
    for(i=2; i<=n; i++)
        v[i]=i;
 
    for(i=2; i<=n; i++)
        if(v[i]==i)
            for(j=i; j<=n; j+=i)
                v[j]=v[j]/i*(i-1);
 
    s=0;
 
    for(i=2; i<=n; i++)
        s+=v[i];
 
    printf("%lld",s*2+1);
    return 0;
    }