#include<cstdio>

int i,j,n,k;
int A[1000005];

int long long S;

int main(){
	
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	
	scanf("%lld",&n);
	
	for(i=2;i<=n;i++){
		A[i]+=(i-1);
		if(A[i]==i-1){
			k=0;
			for(j=2*i;j<=n;j+=i){
				++k;
				A[j]-=k;
			}
		}
		S+=(int long long)A[i];
	}
	
	printf("%lld",2*S+1);
	
}