Tutorial suggestion !

Can anyone please suggest me a way to ADD ,SUBTRACT , DIVIDE ,MULTIPLY (with code) very large numbers in C++14 (like having hundreds of digits each) ,I am a newbie and often encountering problems related to it, so please help me out ..

The link for the problem PROBLEM

In this problem i found the XOR value of the (m+1)th player and each of the players m players from (1 to m) ,and found the number of 1's in the

binary form of the XOR output value.if the number of 1's are less than K then i incremented the counter.

but the approach is giving me wrong answer!

any suggestions to approach??

OR

Can anyone post a link or explain me an efficient way to convert a number from decimal to binary using bitmasks!!