#include <stdio.h>
#include <stdlib.h>

int main()
{
    int n;
    long long int S=1;
    int *fi=(int *)malloc(1000001*sizeof(int));
    freopen("fractii.in","r",stdin);
    ///freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;++i)
        fi[i]=i;
    for(int i=2;i<=n;++i)
        if(fi[i]==i)
            for(int j=i;j<=n;j+=i)
                fi[j]-=fi[j]/i;
    for(int i=2;i<=n;++i)
        S+=2*fi[i];
    printf("%i",S);
    return 0;
}