#include <fstream>
long long s['썐'],n,i,j,r;std::ifstream f("fractii.in");std::ofstream g("fractii.out");int main(){f>>n;for(i=2;i<=n;i++)s[i]=i-1;for(i=2;i<=n;i++){r+=s[i];for(j=i+i;j<=n;j+=i)s[j]-=s[i];}g<<r*2+1;}