Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.3.2)
// ----

@function nth-selector($str, $n) {
  @for $i from 1 through $n {
    @if (str_index($str, ' ')) {
      @if $i == $n {
        $str: str_slice($str, 0, str_index($str, ' ') - 1);
      } @else {
        $str: str_slice($str, str_index($str, ' ') + 1);
      }
    }
  }
  @return unquote($str);
}

.grand-parent {
  .parent {
    content: '' + nth-selector(#{&}, 1);
    
    #{nth-selector(#{&}, 2)} .cc {
      width: 20px;
    }
    
    @at-root #{nth-selector(#{&}, 2)} .cc {
      width: 10px;
    }
  }
}

SassMeister-output.css

.grand-parent .parent {
  content: ".grand-parent";
}

.grand-parent .parent .parent .cc {
  width: 20px;
}

.parent .cc {
  width: 10px;
}