#include <stdio.h>

int main() {
    int N, i, j, fi[1000000];
    long long count = 1;
    FILE* in = fopen("fractii.in", "r");
    FILE* out = fopen("fractii.out", "w");
    fscanf(in, "%d", &N);

    for (i = 1; i <= N; i++) {
        fi[i] = i - 1;
    }
    for (i = 2; i <= N; i++) {
        count += 2 * fi[i];
        for (j = 2 * i; j <= N; j += i) {
            fi[j] -= fi[i];
        }
    }

    fprintf(out, "%lld", count);

    fclose(in);
    fclose(out);

    return 0;
}