Can any body help me know why this adds 3multiple times instead of adding 10

Question

a = [0,1,2,3,4,5]
S=0
for n in a:
S += n
if(n==3):
a.insert(n,10)
if(S>15):
break
Print(s)

Answer 1

Because whenever n is 3, a 10 is inserted at the spot where 3 is.

Which means that 3 shifts one slot to the right.

Which means that in the next loop we'll meet that 3 again.

Answer 2

Thanks HonFu