void stergere_element(int *n, int A[20])
{
    FILE *f = fopen("stergere.txt", "w+t");
    int i;
    for (i = 1; i < *n; i++)
    {
        A[i - 1] = A[i];
    }
    (*n)--;
    for (i = 0; i < *n; i++)
    {
        fprintf(f, "%d ", A[i]);
    }
    fclose(f);
}