i:[1 4 8 7 2 1]; input
l:[6]; length
a:1; at
s:1; swap
c:1; current
d:1; different

; new run
4a+l
a-1
i>
d-d

; compare
2s-s
s+i
s+1
i<
s-i
sn3

; swap
d-d
dvi
i>
svi
i+d
i<
ivs

; next
3i>2
a-1
an2

; changed
1dn4
i=