#include <stdio.h>
#include <stdlib.h>

#define N 1000001

int e[N];

int main() {
    int n, i, j;
    long long int s;
    FILE *fin, *fout;
    fin = fopen("fractii.in", "r");
    fscanf(fin, "%d", &n);
    for (i = 2; i <= n; i++) {
        e[i] = i;
    }
    for (i = 2; i <= n; i++) {
        if (e[i] == i) {
            for (j = i; j <= n; j += i) {
                e[j] = e[j] / i * (i - 1);
            }
        }
    }
    fout = fopen("fractii.out", "w");
    s = 0;
    for (i = 2; i < n + 2; i++) {
        s = s + e[i];
    }
    fprintf(fout, "%lld", 2 * s + 1);
    fclose(fout);
    return 0;
}