This is the most dangerous problem in mathematics. Here’s how it works. Pick a number — seven. (you can take any number). Now apply two rules: 1. If the number is odd, multiply it by 3 and add 1.  3 × 7 = 21, plus 1 = 22 2. If the number is even, divide it by 2.  22 ÷ 2 = 11 Now we keep applying the rules: 11 is odd → 3 × 11 + 1 = 34 34 is even → 34 ÷ 2 = 17 17 is odd → 3 × 17 + 1 = 52 52 → 26 → 13 13 → 40 40 → 20 → 10 → 5 5 is odd → 3 × 5 + 1 = 16 16 → 8 → 4 → 2 → 1 Now 1 is odd → 3 × 1 + 1 = 4 But 4 → 2 → 1 So we are in a loop: 4 → 2 → 1 This is known as the Collatz conjecture and says that every positive integer, if you apply these rules, will eventually fall into the 4 → 2 → 1 loop.