Im kinda novice with c++ , I can work with while/for/if , that basic stuff , and I can work with subprograms & very little with classes I wanna go deeper , I wanna find out new stuff , what would you suggest me ? as this thread is entitled "c++ problems" the main problems have to follow so I finished 9th grade & I was at few c++ competitions there was a problem that got my attention : so you get 2 numbers , a & b , and between those 2 numbers you have to calculate the smallest number with the largest number of divisors & if there are more than one , to count them I watched the tests & for a maximum of 100 points , the last test gave a range of 999999000 - 1000000000 Im not asking you to solve the problem for me , Im just asking how it is possible to count the divisors of such large numbers in just 1 second ?? I would understand if it was only one number but in this range there are 1000 big ass numbers & on top of that you have to do comparations & all that stuff are there any secret algorithms or anything like that that would boost the speed ?? also if you could link me to some places where I could learn the cstdio that would be great thanks !