Combination of two integer array

Question

I have two list of int array, say Input1 and Input2. 

List<int[]> Input1;
List<int[]> Input2;

Data in Input1 would look be - {1,2,3},{4,5,6},{8,9,10}
Data in Input 2 can be {11,12,13},{14,15,16}

The final combined result should be look like - {1,2,3,11,12,13}, {1,2,3,14,15,16},{4,5,6,11,12,13},{4,5,6,11,12,13},{8,9,10,11,12,13},{8,9,10,14,15,16}

How can I achieve that? Also is there any efficeint way to solve this, since I will have few hundreds of int array on both Input1 and Input 2 list.