#include<cstdio>
int n,v[1001000],i,j;
long long nr;
FILE *f,*g;
int main(){
    f=fopen("fractii.in","r");
    g=fopen("fractii.out","w");
    fscanf(f,"%lld",&n);
    for(i=2;i<=n;i++){
        v[i]=i-1;
    }
    for(i=2;i<=n;i++){
        for(j=2*i;j<=n;j+=i){
            v[j]-=v[i];
        }
        nr+=v[i]*2;
    }
    fprintf(g,"%lld",nr+1);
    fclose(f);
    fclose(g);
    return 0;
}