#include <stdio.h>
#include <math.h>

int main() {
    FILE *in = fopen("fractii.in", "r");
    FILE *out= fopen("fractii.out", "w");
    int N;
    fscanf(in,"%d", &N);
    long long int count=1;
    for (int i=2; i<=N; i++) {
        long long div = 0;
        for(int j=2; j<=sqrt(i); j++){
            if(i%j==0) div++;
        }
        count+= 2*(i-1-div);
    }
    fprintf(out, "%llu\n", count);
}