hi everyone! i was trying this problem HENRY:- Henry and Lost Ranges

Henry is a curious little boy. He likes to play around with numbers. One day, he defined a fun ction f for natural numbers such that: f(X) = largest prime factor of X , where X > 1 For example: f(2) = 2 f(3) = 3 f(75) = 5 Now, Henry selected two integers A and B ( A ≤ B ) and counted all numbers X between A and B (both inclusive) such that f(X) = K . He found out that there are N such numbers. After that Henry went for playing. When he returned home, he found out that he had forgotten the upper limit of range i.e. the integer B . However, he remembers all other numbers i.e. A , K and N . Henry wants to find out B as soon as possible. Can you help him finding it ? Note: ● If there are multiple possible values of B , output the least value out of those. ● It is assured that the input will be in such a way that final value of B will be within the range of long long int . Input First line of input contains T , the number of test cases. The only line of each test case contains three integers A , K and N . Output For each test case, output a single line containing the integer B . Constraints ● 1 ≤ T ≤ 5 ● 2 ≤ A ≤ 10 9 ● 2 ≤ K ≤ 11 and K is a prime number ● 0 ≤ N ≤ 152319 Example Input: 5 3 2 4 5 3 4 4 5 4 5 7 4 3 11 4 Output: 32 18 20 28 44 Explanation In the first case, least value of B such that there are exactly 4 numbers having largest prime factor as 2 in range [3,B] will be 32 (the 4 numbers are 4, 8, 16, 32 ). In the second case, least value of B such that there are exactly 4 numbers having largest prime factor as 3 in range [5,B] will be 18 (the 4 numbers are 6, 9, 12, 18 ). In the third case, least value of B such that there are exactly 4 numbers having largest prime factor as 5 in range [4,B] will be 20 (the 4 numbers are 5, 10, 15, 20 ). In the fourth case, least value of B such that there are exactly 4 numbers having largest prime factor as 7 in range [5,B] will be 28 (the 4 numbers are 7, 14, 21, 28 ). In the fifth case, least value of B such that there are exactly 4 numbers having largest prime factor as 11 in range [3,B] will be 44 (the 4 numbers are 11, 22, 33, 44 ).

my solution:- http://pastebin.com/VccNHSwz since k is <= 11 hence we have primes 2,3,5,7,11 only.. for a particular k i need to check only the numbers formed with combinations of all prime numbers<=k for example.. if k=5 then 2^a*3^b*5^c where c>=1 and a>=0 and b>=0.. so i precomputed all such numbers for all k in <=100000000 then i applied lower_bound to find the least b i am getting wrong answer although i think i have handled overflows correctly! please someone help me understand my mistake! PS:- code is lengthy because but very easy to understand