bit complement operator in euclidean division

https://math.stackexchange.com/questions/679146/euclidean-divison-program did not answer this query. I learnt that, Given two integers a and b, with b ≠ 0, there exist unique integers q and r such that a = bq + r and 0 ≤ r < |b|, where |b| denotes the absolute value of b - Definition euclidean division Corresponding program that implements this logic is as shown below: ``` int ifloordiv(int n, int d){ if (n >= 0) return n / d; else return ~(~n / d); } ``` After reading the above code, It look obvious for me to understand if(n>=0){} block code logic that we are doing real division not euclidean. But, else{(n<0)} code logic using bit complement operator(~) was not looking obvious to me to understand the thinking approach behind usage of ~ operator. Generally we use >> operator when we think of division. I know that java ~ operator is 1's complement operator on integral types. My question is: I would like to understand the thinking approach on, How can i think of using bit complement operator(~) that it helps you to perform euclidean divison when n<0. Because it was not obvious for me to think on using ~ operator. Please help me tune my approach.