Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

remainder

The leftover from whole-number division, written with %, so 7 % 2 is 1.

For integers, a % b is a - (a / b) * b; its sign follows the left operand.