#include <cstdio>
int f[1000000];
int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int n,i,j,rez=1;
    scanf("%d",&n);
    for (i=1;i<=n;++i){
        f[i]=i-1;
    }
    for (i=2;i<=n;++i){
        for (j=i+i;j<=n;j+=i){
            f[j]-=f[i];
        }
    }
    for(i=1;i<=n;++i){
        rez+=2*f[i];
    }
    printf("%d",rez);
}