Like the title stated. I really need help with this problem. It's in my training camp for my country's national olympiad. I'll simplify it for you guys. Given three numbers X,Y,Z (X,Y,Z <= 9000), Count all divisors of all number that is a product from three numbers a,b,c such that (a <= X,b <= Y, c <= Z) and modulo 2^30 To be more clear,a simple algorithm to solve it is: res = 0 for i = 1...X for j = 1...Y for k = 1...Z res = res + count_divisors(i*j*k) count_divisors is a function that counts all positive divisors of an integer It's obviously too slow Find res modulo 2^30 Time limit is 2 seconds. It's quite ridiculous guys. Thank you for any help!