#include <stdio.h>

char prim[1000000];

int main() {
    int N, i, j, count, prime = 0;
    FILE* in = fopen("fractii.in", "r");
    FILE* out = fopen("fractii.out", "w");
    fscanf(in, "%d", &N);

    count = N;
    for (i = 2; i <= N; i++) {
        if (prim[i] == 0) {
            prime++;
            for (j = 2 * i; j <= N; j += i) {
                prim[j] = 1;
            }
            count += N - N / i;
        } else {
            count += prime;
        }
    }

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

    return 0;
}