push_front:1
New Stack: 1
push_front:2
New Stack: 2 1
push_front:3
New Stack: 3 2 1
push_front:4
New Stack: 4 3 2 1
push_front:5
New Stack: 5 4 3 2 1
back:1
New Stack: 5 4 3 2
push_front:6
New Stack: 6 5 4 3 2
back:2
New Stack: 6 5 4 3
push_front:7
New Stack: 7 6 5 4 3
back:3
New Stack: 7 6 5 4
push_front:8
New Stack: 8 7 6 5 4
back:4
New Stack: 8 7 6 5