int i = 0, j = 0;
    while (k < n)
    {
        k++;
        for (j = k - 1; j < n - k + 1; j++) {
            mas[k - 1][j] = number++; i++;
        }
        for (j = k; j < n - k + 1; j++)  {
            mas[j][n - k] = number++; i++;
        }
        for (j = n - k - 1; j >= k - 1; j--)  {
            mas[n - k][j] = number++; i++;
        }
        for (j = n - k - 1; j >= k; j--)  {
            mas[j][k - 1] = number++; i++;
        }
    }