1st list [A,B,C,D,E,F,G]

2nd list [1,2,3,4]

How to put every n item in the 2nd list after every m items in the 1st list?

If n=1, m=1, the result should be [A,1,B,2,C,3,D,E,F,G]

If n=1, m=2, the result should be [A,B,1,C,D,2,E,F,3,G]

If n=2, m=1, the result should be [A,1,2,B,3,4,C,D,E,F,G]

If n=2, m=2, the result should be [A,B,1,2,C,D,3,4,E,F,G]