#include <cstdio>

FILE*f=fopen("fractii.in","r");
FILE*h=fopen("fractii.out","w");

long long e[1000001];

int main(){
    int n;
    fscanf(f,"%d",&n);
    for ( int i=1;i<=n;++i ){
        e[i]=i;
    }
    for ( int i=2;i<=n;++i )
        if ( e[i]==i )
            for ( int j=i;j<=n;j+=i )
                e[j]=e[j]/i*(i-1);
    for ( int i=1;i<=n;++i ){
        e[i]=e[i-1]+2*e[i];
        //fprintf(h,"%d\n",e[i]-1);
    }
    fprintf(h,"%lld",e[n]-1);
    return 0;
}