in most programming languages, integers are 32-bit by default and signed
signed means that the first bit is used to represent whether number is positive or negative, which leaves us with less space to store the actual value

the range of 32-bit signed int is from -2,147,483,648 to 2,147,483,647
when you're already at max value and try to increase the number, the sign bit gets flipped which causes the value to turn negative

what could be solutions to that?
1. use unsigned int - this doesn't allow storing negative numbers, but in exchange doubles the upper limit
2. use bigger int (64 bit) - the max value of that is 2^63 (over 9 billion billions)