Figure 2

Stack contains:    0   0   0   0      sp1 = 0, sp2 = 3
Stack contains:   10   0   0   0      sp1 = 1, sp2 = 3
Stack contains:   10   0   0  12      sp1 = 1, sp2 = 2
Stack contains:   10  15   0  12      sp1 = 2, sp2 = 2
Stack contains:   10  15  34  12      sp1 = 2, sp2 = 1
Stack 1 is full
Stack contains:   10  15  34  12      sp1 = 2, sp2 = 1
Stack 2 is full
Stack contains:   10  15  34  12      sp1 = 2, sp2 = 1
stack 1: 15
Stack contains:   10  15  34  12      sp1 = 1, sp2 = 1
stack 1: 10
Stack contains:   10  15  34  12      sp1 = 0, sp2 = 1
Stack 1 is empty
stack 1: 0
Stack contains:   10  15  34  12      sp1 = 0, sp2 = 1
stack 2: 34
Stack contains:   10  15  34  12      sp1 = 0, sp2 = 2
stack 2: 12
Stack contains:   10  15  34  12      sp1 = 0, sp2 = 3
Stack 2 is empty
stack 2: 0
Stack contains:   10  15  34  12      sp1 = 0, sp2 = 3