#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;
    }