#include <cstdio>
using namespace std;
typedef long long i64;

const int NMAX = 1000005;

i64 phi[NMAX];

int main(void) {
    FILE *fi = fopen("fractii.in","r");
    FILE *fo = fopen("fractii.out","w");
    int n;
    i64 ans;

    fscanf(fi,"%d",&n);

    for(int i=1; i<=n; ++i)
        phi[i]=i;

    for(int i=2; i<=n; ++i)
        if(phi[i]==i)
            for(int j=i; j<=n; j+=i)
                phi[j]=phi[j]*(i-1)/i;

    ans = 0;

    for(int i=1; i<=n; ++i)
        ans+=phi[i];

    fprintf(fo,"%lld\n",2LL*ans-1);

    fclose(fi);
    fclose(fo);

    return 0;
}