ProfessorZoom

Here it is in c++, 25 lines that demands a correct octet before moving on like you said.
#include <iostream> #include <string> int main() { int octet; std::string ipAddress = ""; for (unsigned int i = 0; i < 4; i++) { std::cout << "Please enter octet #" << i + 1 << ":\n"; do { std::cin >> octet; if (!(octet >= 0 && octet <= 255)) std::cout << "That octet is invalid. Please try again.\n"; } while (!(octet >= 0 && octet <= 255)); ipAddress += std::to_string(octet) + "."; } std::cout << "IP Address: " << ipAddress << "\b \n"; system("pause"); return 0; } /* Please enter octet #1: 1 Please enter octet #2: 2 Please enter octet #3: 3 Please enter octet #4: 4 IP Address: 1.2.3.4 Press any key to continue . . . */  

Hey everyone! ?
 
I'm here to talk to y'all about Cancer, Alzheimer's, Huntington's disease, Parkinson's. They're are all terrible diseases that have had an affect on nearly everyone in one way or another, and we want to help. Researching these conditions in an attempt to cure them is an incredibly expensive endeavor, but for many people, donating to fund these causes isn't an option. Thankfully, there is still something we all can do: Folding @ Home
 
With your gaming PC, laptop, server, or really any computer, you can donate processing power from your CPU or GPU when you're not using them to help run calculations on a vast number of distributed computation projects. This massive shared computational power can help researchers learn more about these diseases in an effort to better treat them, and it can make a HUGE difference in the fight to conquer them. To achieve this huge collaborative effort, Stanford University started developing the Folding @ Home project, all the way back in the year 2000. It's a simple software you can run on your PC that automagically uses your processing power when idling (or full time if you desire) for the previously mentioned calculations. 
 
In exchange for your valiant processing effort, you can earn points that show off your contribution to find the cures, in the form of a friendly competition. The LinusTechTips community & forum has had a folding team, number 223518, since 2013 and we'd love for you all to join it!
 
You can fold with pretty much anything, your dad's old dell prebuilt, a top tier RTX rig, or presumably even a Raspi. Every little bit helps
 
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To help promote the project we're going to give away a couple awesome prizes! ?
 
#1 - NVIDIA GTX 1080
For this GPU, we will be picking someone randomly in the top 100 lifetime folders on the LinusTechTips team. This one will cater a bit to the long time folders. #2 - Two NVIDIA GTX 1070's
For each of these GPUs, we will put up an entry form on November 23rd, 2018 at 11:00 AM PST where you will be able to submit a link to your folding profile as well as a photo of your folding rig and we will select 2 random winners from these submissions. Entries will close on November 30th, 2018 at 11:00 AM PST. Entries have closed.  
Contest Info:
 
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The goal for the Folding @ Home project this year is to have 1 million concurrent folders, so get on there and start folding!
 
Downloading Folding @ Home: https://foldingathome.org/start-folding/
Set your username to same as your forum handle, the team number to 223518, and a passkey can be generated here: https://apps.foldingathome.org/getpasskey  
More Information: https://linustechtips.com/main/topic/876-foldinghome-install-guide-and-links-linustechtips_team-223518/
Monthly Leaderboard: https://stats.foldingathome.org/teams-monthly
LinusTechTips Folding Team: https://stats.foldingathome.org/team/223518
 
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Also, if you want to sign up for the official LTT Folding month competition, entries close on November 6th, 2018 (this is seperate from the GPU giveaway/contest)
Sign up now: https://goo.gl/forms/u5HJRQ8M2kBxJwik2  
Be sure to post photos of your folding rigs, your progress, and any questions below!   (We've got a rig running with two 1080s, a 1080 Ti, and a Titan X pascal) 

Here is a digital square root calculator in 26 lines.
 
#include <iostream> #include <string> unsigned digitalRoot(std::ostream &ostr, unsigned input) {     unsigned root = 0;     while (input > 0)     {         unsigned digit = input % 10;         root += digit;         input /= 10;         ostr << digit << " + ";     }     ostr << "\b\b\b = " << root << std::endl;     return root < 10 ? root : digitalRoot(ostr, root); } int main() {     std::string input;     std::cout << "Please enter a number: ";     std::getline(std::cin, input);     std::cout << "\nDigital root is " << digitalRoot(std::cout, (unsigned long long)std::stoi(input)) << ".\n\n";     main();     return 0; }

The last thing I bought, yesterday, was four comics.
 

The last thing I bought, yesterday, was four comics.