#include <stdio.h>

long long calc(n){
    int i = 0,j = 0;
    int x[n+1];
    long long result = 1;
    for(i=0;i<=n;i++) x[i] = 0;
    for(i=2;i<=n; ++i) x[i] = i-1;
    for(i=2;i<=n; ++i){
	result += 2 * (long)x[i];
	for(j = i * 2;j<=n; j+=i){
	    x[j] -= x[i];
	}
    }
    return result;
}

int main(){
    FILE *f = fopen("fractii.in","r");
    int n;
    long long res = 0;
    fscanf(f,"%d",&n);
    fclose(f);

    res = calc(n);
//    printf("%lli \n",res);
//    return;
    f = fopen("fractii.out","w");
    fprintf(f,"%lli",res);
    fclose(f);
    
}