678A - Вася любит числа
The problem was suggested by Abdrakhman Ismail bash.
We should find minimal x, so x·k > n. Easy to see that . To learn more about floor/ceil functions I reccomend the book of authors Graham, Knuth, Patashnik "Concrete Mathematics". There is a chapter there about that functions and their properties.
Решение на С++
Complexity: O(1).