[alt text](image url)

Guys As i have found most difficulties to understand the problem.Here From the above picture we can see that the product of ith and jth number will be stroed in position i+j and i+j+1,

i.e., res[i+j] is used to store the carry value and res[i+j+1] is used to rightmost digit of the sum.

I hope it will help you.