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




    fclose(f);
    fclose(g);
    return 0;
}